And, if they make a wrong entry or get confused, and you say "It's 13 cents", they look at you with puzzlement and ask, "How did you do that?"
My second job was at a busy (self-service) gas station. I’d work the weekends, opening up, and doing the 4am-noon. You had to think quick in that job because people would literally be tossing you money holding up a cup of coffee and a newspaper while 6 people had to have their pumps turned on, and four more people were in line.
I often give cashiers money so that I get $5 or $10 bills back, so if something is say 12.73, I give them $23. They usually look like ‘deer in headlights’ for a few seconds and say “No, it is just 12.73”. “I know, but I want a $10 bill back” “Uh...ok. Wow, how’d you do that?”
The first time that happened *I* had the deer in headlights look.