Something like that happened to me once -- it was before gas went sky-high:
I'll say the gas was something like .95/gallon . . . I saw .95 on the sign by the road and pulled in -- back in those days I didn't pay much attention to gas prices. I started filling my tank, and I realized that the pump said .05, but I'd already started filling, so I finished.
When I went in to pay (this was before pay-at-the-pump), the clerks realized something was wrong because the total was something like fifty cents. They realized that the gas should've been .95/gallon, and they knew that I'd bought 10 gallons -- now here comes the good part:
The two clerks talked and talked, unable to figure out how much I actually owed. I just stood there, shocked that they couldn't figure out .95 x 10 gallons = $9.50. I wasn't going to help them. Finally one of them said, "Would you just pay three dollars?" And I said, "Sure."
Come on, folks, math matters. That's just plain old arithmetic.