You are correct. Most cashiers have no trouble swiping the card and giving you a receipt. But give them a $20 for a $7.67 bill and they’re likely to freeze up, then attempt to give you some bills and coins in the hope that it’s close. I recently gave a cashier $20.24 for a $12.24 bill. I received nine dollars and some change in return.
My favorite cashier story was in the NY Times years ago. A man bought some things at the store and the cashier told him the total was ten sixty-six. He responded “Ah, the Battle of Hastings.” She looked at him funny and said, “What?” He explained. She was quiet for a while and then said, “Can you do that with any number?”