At the local grocery store there is one bagger who is ultra-slow, who is far from being on the last bag once I’m done paying. And when I start to grab the unbagged stuff and just put it in my cart to speed things up, he stops what he’s doing in confusion and stares at me. Thankfully I haven’t run into him lately, but if I do I will try to use a different lane.
I occasionally get a cashier who tells me to “have a blessed day”.
Never felt the compulsion to respond.
Him: “God Bless!”
You: “Have a good night.”
Done.
Unless you don’t wish him a good night because he mentioned God?
I used to occasionally shop at a grocery store that had a mentally disabled bagger. That in itself doesn’t bother me, but in this case, she really wasn’t capable of doing the job. 
I didn’t go through her lane if I saw her.
I’ve recently moved to a new area of town and started frequenting a different grocery store. The express lane seems to be staffed often by an elderly lady who chats moderately but not too much. Only recently have I begun realizing she ends every transaction by saying “Uh-huh…sure!” while turning her attention to the next customer. It’s seems to be an amazingly versatile and generic phrase. She hands back change along with a receipt with a “Thank You!” and then, regardless of the departing customer’s response, her phrase seems appropriate.
“Thank you.”
“Uh-huh…sure!”
“Have a nice weekend.”
“Uh-huh…sure!”
“I’ll see you next week, same time, same stuff.”
“Uh-huh…sure!”
“Don’t forget to feed the homeless people behind the store after you clock out.”
“Uh-huh…sure!”
—G!
Where I shop, there’s one cashier who looks like he’s the next person to go postal. Nothing particular about him, but I’m actually afraid that if I get in his lane, I’ll say or do something that will set off his short fuse. Lately, I’ve discovered that I’m not the only one who avoids his aisle.
“Hail Satan!” Or even better, “Will do.”
I like the not-exactly-right “and also with you”
This is why G-d made “You Check It” thingies.
I don’t think I’ve been in a store without it for close to 15 years. Unfortunately, there are a couple stores where the 1 person who watches the self-checkouts is very invasive. This one guy always looks at my stuff and asks me random questions. Another uses (or has) a cartoon voice and makes random noises.