If you give it to a bona fide charitable organization, then yes, you're allowed to deduct the fair market value of the car as a donation (provided you itemize deductions). If that's not what you were...
Go to DMV.org and it will calcluate it for you. like for example if you were in CA here is the website: http://www.dmv.ca.gov/FeeCalculatorWeb/index.jsp Or maybe type Fee Calculator or Vehicle...
In buying a car the tag and title are a set price set forth by the state with a very small difference based on the person doing the notary work. Find out what that dealership charges. In most places...