For example, give them four quarters instead of one dollar.
As many people prefer not to carry around lots of loose change, they’re more likely to just drop it in your tip jar.
As an added bonus, there will be less coins in the register to count at the end of the day, if that’s part of your job.
When you look for the change in your purse, take extra time to do it until the customer gets impatient and says “Keep the change!”
even better!
Stare blankly at them and say “I keep”