What you are probably interested in is calculating the house edge, or expected value, from playing the game. Probability of winning can also be calculated but isn't that helpful.
http://www.quora.com/Probability/Howwouldonecal...

Generally, most organizations count a tie a one half win and one half loss when computing winning percentage. The National Football League is one of the organizations that does this
http://wiki.answers.com/Q/How+do+you+calculate+TIE

To calculate winning percentage you take wins divided by total games.
http://www.chacha.com/question/howiswinningperc...
