Bought a watch battery once. Lovely young shopgirl, well groomed, well spoken, polite and cheerful. Told me the battery was $ 7.99 and asked if I wanted it. Said yes - she took my watch and proceeded to put the battery in.
While her back was turned I fished around in my pocket and found
$ 8.48 in bills and coin. (Sales tax rate where I was at 6%) She hands me my watch and I hand her the money. She asks me "Whats this for?" "To pay you", I answer.
She takes the money and rings up the sale, looks at the register in wonder. As she hand me the reciept she asks "How did you do that?"
"Do what?"
"Know how much to pay>"
Told her I just figured it out in my head. She looks at me and says, "Wow - you must be a genius."
Now in all my life, having been called many things by young women, that is the first time I have ever heard the word "Genius" applied to me!