If you itemize your deductions, and if you live in a state with no income tax (or your sales tax is higher than your income tax), you might benefit from deducting sales tax on the purchase of the car. Enter the expense in Turbotax and the program will tell you what gives you the lowest income tax.
For the sales tax deduction, you can either deduct the actual amount of sales tax you paid for the whole year that you can prove with reliable records, or you can use a "standard" amount provided by the IRS based on your local tax rates and your income. If you use the standard method, you can add sales tax you paid for purchase of a motor vehicle.
However, you can only deduct general sales tax that is charged at the same rate on every other purchase in your area. For example, if the general sales tax rate is 4% for the state and 3% for your county, that's what you can deduct on the purchase of the car. You can't deduct most other taxes and fees, such as a registration fee, road tax, etc.
Separately, if you are charged a personal property tax (value tax, ad valorem tax) based on the value of the vehicle, that is also deductible, but not in the sales tax section, it is in the personal property taxes section. But again, only the part that is based on value. For example, in my county, I was charged $350 last year on the value of my used car, $330 based on the value and a fixed $20 fee. The deductible amount is $330, not $350.
