Tournament win rate accuracy

[Homer]

I've recently started playing some single-table tournaments online. I was wondering how I might go about computing the accuracy of my win rate. I'd like to be able to make a statement like:

"There is a x% chance that my win rate is between $y and $z per tournament."

Background information on the tournaments -- Ten players, buy-in is $33, 1st pays $150, 2nd pays $90, 3rd pays $60.

-- Thanks, Homer