tipping w/other ppl's money (coworkers, boss)

[The Owl]

Ask the person giving you the money how much you should tip.

Didn't want to start my own tipping thread, so here's my recent tipping issue:

My doctor's office is in a big medical building. When you pull into the underground garage you're required to leave your car with the valet, they're right at the entrance. The doctor does not validate. I was there on Monday for 40 minutes and was charged $9 to park my car. Let me reiterate I did not choose to valet the car, I didn't have another choice. I did not tip the valet the extra $1, my wife said I was being a douche. Thoughts?