A closed till can end a transaction while a badly handled exchange continues traveling.

Business ends faster than feeling does. The payment clears, the shutters come down, and whatever happened over the counter carries on into somebody’s evening, gets told to two people at home and decides whether they ever come back. The transaction took ninety seconds; the impression did not. That asymmetry is easy to miss from behind the till.

If you serve people, treat the last ten seconds as the part that travels. If you were on the receiving end of something graceless, you are allowed to say so once and then set it down. Not everything that follows you home needs to stay the night.