I don't like seeing a tip jar at retail stores that aren't sit-down restaurants, and I refuse to use them.

However, I did make an exception recently (between Christmas and New Year's): I put a few bucks in the tip jar at the medical marijuana store because I was feeling generous, and I did say "happy new year, and merry christmas" (can't say it the other way around if it's after Dec. 25). The two ladies working there were very happy!