You should not feel obligated to chunk your change into a tip jar but if you are with a client and want to add to a tip jar for the sake of appearances, add a dollar bill, not your spare change.

你不必认为往小费盒里放钱是你的义务。但是当你和客户一起时，为了引起注意，可以放一美元进去，但是不要放零钱进去。

youdao

For the sake of appearances, it wrote, Mr Zhou would continue making public speeches and taking official meetings in other words, even the study of photographs would not reveal his real fate.

ECONOMIST: Banyan