The person ringing you up has plans, problems and a playlist too. A real “thank you” costs nothing.

It takes effort to remember that the people doing jobs around you are in the middle of their own day, with a shift that ends, someone they are worried about, and music they were listening to before they clocked in. Most of the time they get treated as part of the process rather than as a person. That is not cruelty, it is speed. Slowing down for four seconds undoes it.

Try eye contact and a thank you with your actual voice in it rather than the automatic one. Once a day is enough. Notice what it does to both of you.