Everyday Ethics with Mrs. Spit

I'm at a tea place, having tea with Kuri, to knit. (And I forgot to give her the prize she won, but I digress)

I go and pay for my tea, and the samosas, which I pick out at the counter, pay for at the counter, and pick up at the counter.

I hand them my debit card, and go through the process until I come to the "tip" screen. Tip? For what? You stood at a counter and you took my order. I did all the work.

I keep wondering? Should I be tipping? When? Did Kuri tip? What should I do here?

For the record, I tip at restaurants, I tip my hairdresser, my paper boy at Christmas, taxi drivers, hotel bellpersons. . . I might even throw some coins in the jar at the local Second Cup Low Altar of Caffeine. Especially when they automatically pour my usual for me. (Not that I'm an addict, nope, not me. Nuh uh).

But really, do I need to tip, when a service person has provided essentially no service? Just doesn't make sense to me.

I keep wondering, what does everyone else do?