Probably just habit. The tellers I've seen are pretty rigorously trained in double-check procedures. If she used a calculator to figure out how many quarters to give you back, though, then I'm scared.

I had a similiar experience. She kept recounting my money trying to make sure it was correct. Thinking she was new, I glanced at her name tag to see if it said something about her being in training. Her name was neatly printed right under the label "Head Teller."

I'm just saying. It was only twenty bucks. It's not like I handed her an envelope full of change and $12 in foreign bills. Sheesh.

(I keep answering comments and then my answers disappear! My own blog hates me!)