I did a search and didn’t turn up anything. Anyway…
For as long as I can remember, gasoline prices end with a .9–three decimal places. Now, since currency only goes two decimal places, this is impossible to pay for. So why was it done?
I think the obvious answer is an extrapolation of the 9s in the price of anything–to make the product appear cheaper (ie $19.99 looks better than $20).
But suppose you buy exactly a gallon of gasoline, for the price of $1.299. You have to pay $1.30 for it. Does that little .001 cent add up over time into some insidiously large amount, like in, say, Superman III or Office Space?
Technically, there is a unit of currency called the mill, which is equivilant to 1/1000th of a dollar. It has never been minted, however. The situation would be comperable to when you want to buy a $19.99 item with a $20 bill and the seller doesn’t have change. Either you pay the $20 or you don’t get the item.
It is set that way because the gas stations actually deal in fractions of a penny when they are buying their gas. You are not physically being ripped off (by most honest stations, anyway) because you can actually squeeze out that extra hundreth of a gallon or whatever before it rolls over to the next cent.
If you pump exactly 10 gallons (or better, exactly 100 gallons) in your tank, you will see that the price indicator does – or at least should – stop exactly on the penny and not roll over.
If you only pump in exactly one gallon of gas, you’re too anal retentive to satisfy.
Some of us can remember the ancient times when gasoline prices were around 25 cents a gallon (and, I’m sure, others can remember when it was even less). A tenth of a cent as a percentage of 25 cents is significantly more than a tenth of a cent as a percentage of 125 cents. So the nine-tenths pricing really makes no sense (pun intended) anymore, it’s continued only out of historical inertia.
To answer the actual question: I think you’ll find that if you tried, you wouldn’t really be able to buy EXACTLY one gallon of gas. You could buy a dollar and twenty-nine cents worth of gas, or you could buy a dollar and thirty cents worth of gas. If you went to a gas station and really REALLY insisted on getting EXACTLY one gallon, I suspect the manager would likely insist back on charging you the dollar thirty and taking the whopping tenth of a cent as pure profit.
But, in general, there’s on Superman III effect because the transaction isn’t based on an even gallon amount it’s based on an even dollar-and-cents amount. (Besides, the Superman III effect is pure fiction anyway).