As we are talking about international travel, a significant difference between US and rest-of-the-world credit card practice. Certainly in Europe the complete amount, including any tips and surcharges, has to be shown on the tab. It's a credit card company requirement. Any tips have to be entered before the transaction is presented for authorisation, nowadays invariably on a hand-held machine, which makes for an amount of forwards-backwards of the machine.

I wouldn't have believed the "stick your own tip on a foreigner who doesn't understand US procedure" if I hadn't seen it myself. One of the mainstream airport hotels, and we are at Miami again, at the morning checkout. The (Scandinavian ?) gentleman in front of me looks puzzled at his bill, and queries the restaurant charge. The folio is produced, with a substantial, maybe $30 tip on it, and totalled. The clerk just says did you write the total in, the man says he just signed it, and the clerk semi-sneeringly says "well, you gotta complete it".