I used to work in a convenience store, back in the 80s, in Las Vegas. A lot of people tried to pay for their purchases with a fifty or hundred dollar bill, even if the purchase was a single can of beer (most single beers cost less than a dollar then). And then they were amazed that we couldn’t make change. Usually, they weren’t trying to scam us, they were just trying to break their bills. Sometimes they were trying to scam us, though.
Here ya go. A perfect, simple example of what happens when the cash handler doesn’t keep control and lets the fast talking take the lead.
It’s disconcerting how many Dopers have me set to Ignore. 
There are several YouTubes demonstrating the scam; why did you have to pick the exact same one I linked to?
Did you want to rub in the fact that you have me on virtual-Ignore? Are you a right-winger, Mr. Tattoo? If not, what did I do to offend you? 
I’ve had the same thought numerous times, where it’s a much-posted thread and my answer was fairly early on, but seemed like no one read it at all. Boo. I used yours because I had already watched it and already had it in my viewing history, so easy to find again and link.
Here’s one from The Riches, a two-fer, so you don’t feel cheated. Your only offense is not having the answer to the volume issue on those You Tubes! Oh, and I’m a Ms., though it seems my moniker is usually taken as masculine.
To be fair, it was a post to a Youtube link, with no description of what it was about, so it’s easy to miss for those (like me) who didn’t click the link. Missing post #29, though, I have no excuse for.
My favorite money-counting trick, courtesy of Harry the Hat.
Anyway, when I worked box office at a movie theater, I quickly learned to set the customer’s money to the side, visible to both of us, before I counted out their change. When there were occasional disputes, I could show them directly what they’d handed to me, since it had never left their sight.
Buying a coffee with a $100 bill? Even regular shops in the UK rarely take £50 notes - I can’t imagine a coffee stand taking at $100 bill.
Yeah, when I was a register monkey, we never accepted 100s and near the end 50s.
I had that happen when I first started working, back when I was in high school. He made off with sixty bucks. (Hey, I was 16 and I had been working there for a month). After that, the rule was if anyone wanted change AFTER you gave them their change back from their purchase (Oh hey, now can you break this fifty for me?) they’d have to go to the service counter.
And when I worked at Kmart, we never gave people change unless they bought something – again, if you just wanted change, even if it was four quarters for a dollar, you had to go to the service desk. I had one old guy call me a bitch over that. Too many scammers ruining it for everyone.
It’s all in the rapid-fire patter and confusion. After a (short) while, you don’t know what you’ve been given back or not. I’ve seen a true artist in action, and it’s something to behold. That’s why we were told don’t even try to outsmart them, just close the drawer and say “No change.”
I don’t think I’ve ever been short changed this way, and around here the “you gave me a ten” ploy would be pretty hard to put over as ten dollar bills are rather rare. I know in at least one recent year the BEP didn’t print any at all. Whoever decides these things apparently has concluded that two fives are almost as easy to handle as one ten, which is pretty much true.
Most folks won’t put the bill into the register. They’ll lay it on the front surface in open view, give out the change and then put the bill in the register. It’s kinda hard to claim I gave you a 20 when your 10 is lying there in plain view.
At such places as fast-food drive-throughs where I hand over a 20, I glance at the serial number and memorize the last four or five digits.
Is anyone else getting ghost text in here?
Me, too. 3425 last week at Taco Bell. Do I win a prize?
You’re still alive?
Yeah, but I need some hot sauce to get goin’ in the AM. 
(Coffee won’t do it anymore.)
Thanks!
Thanks to you too – sorry I missed it the first time.
For your next experiment, you can put pepper spray on Taco Bell offerings. 
The scam artist simply waits till the drawer is closed to mention it. Stay sharp and call out the amount tendered and you’re probably safe. Like with any scam, the thief relies on the victim not paying attention or slipping up somewhere.
Around here, the one that makes my own blood boil are cons preying on the elderly. Typical scenario: "Ding-dong. Hi, I noticed your electrical wires are getting pretty saggy and close to the trees. Here, I’ll show you,’ While they go look, an accomplice enters the still-open front door and steals the senior’s life savings and heirlooms. All the elderly widow had to do was pull the door shut behind her but, based on my local police blotter, the scammers are pretty slick.
Folks, I come off as a real grinch in this thread.
I’ve spoilered my reply to minimize the hijack damage.
I know my ‘didn’t I give you a twenty’ is funny because I only use on those who find it funny.
If I did it to you, you’d laugh but I probably wouldn’t do it to you because you probably won’t make make the cut.
I don’t go around the Midwest leaving a trail of fresh faced kids on after school work permits in tears and jobless for some sort of amusement.
My in-person demeanor is much more polite than my message board posting style and i think I’m pretty nice around here.
The set up is a being personally helped in a quiet store, light hearted goofing off with the staff member to establish they play ball & they’re not a pants wetter and an observing coworker/superior around to rule out any actual appearance of fraud or theft.
Walgreens clerk? No good for all three reasons.
Grocery checker? Same deal.
Dunkin Donuts cashier? May have other coworkers around but without the goofy back and forth, it isn’t suitable.
Hardware store guy helping me find the god damned pipe thread adapter that I know you must have since they’re both common sizes and he finds it in a minute in the wrong slot and makes a sarcastic but deserved and accurate remark? Bingo.
For the record, I worked retail for a period of my formative years and absolutely loved it. I didn’t use the ‘quiet bike shop or bar’ examples by accident, I worked both of these jobs (Ok, coffee bar) and really, really enjoyed it. Why? Mostly because of the characters.
Here’s a couple examples of jokes played on customer by employees that I recall. One was played on me and the other, I just witnessed but I hope they illustrate the idea I’m probably poorly trying to present.
I went away to school in Milwaukee and at times, I’d take the Amtrak to or from Chicago for weekends or breaks.
There was a uniformed staff member (conductor, steward, car attendant?) who’d walk back through the train selling drinks and snacks. He had schtick till year’s end and a mustard bottle gag that killed. It was a bright yellow string in a plastic mustard bottle that, when squeezed, appeared to be a string of mustard flying at ya. I saw this 6-8 times and the results were anything from half the car cracking up to isolated squeals of laughter. Always a hit.
On its face, this is cruel behaviour, right?
Worse than Uday, Qusay and Saddam, all rolled into one.
I mean, that moment where you think your clothes are ruined is awful.
But no, this guy was funny and smart and had the personality to make it work. I doubt he ever got a single complaint or it never could have continued. He had obviously been doing this for years.
Another prank he pulled was selling a bag of Doritos he’d emptied and glued back shut.
But here’s the thing: He never tried it on me. I was travelling alone, didn’t fit the profile and wasn’t a candidate for his funny.
As far as he knew, I might get annoyed and that wasn’t what he was going for at all.
Here’s the one that did happen to me.
I drove to a show several states away after work and got in late to the hotel. The front desk guy asked how my trip was and where I was coming from, was I in for the show, etc while I filled out the papers.
“I’m sorry, your card has been declined.”
Inner dialog: “What the hell, no way, holy crap…whaaaa?”
Looking back up at him, he was smiling.
He got me. Tricked me good. I would have playfully punched him in the shoulder if he wasn’t across the counter.
If he did this to the wrong person, he’d be gone. But he sussed me out, saw I was an appropriate goat and I remember it fondly to this day.
Anyhow, I realize that it is satisfying to call out an asswipe and based on my description, you might not be wrong. I might have reserved some of the frothier responses for a brandished pistol but I fully understand the basis. I wanted to take a moment to better explain what really happens.