dentist90,
I would go to edmunds.com and arrive at a price. This site allows you to pick the make, model, color, and options and shows what others are paying for the same automobile in your area. I used this strategy when buying my last new vehicle. Upon going to the dealership I simply handed them the 'out the door' price that I was willing to pay. They laughed and then argued but upon my leaving they accepted the deal.
To answer your original question... from what I have read the dealers actual profit is around 4% to 5%; however, I find this low margin extremely hard to believe.
http://www.edmunds.com/