Your question has several layers, you may not realize or you are not clear on.
If you itemize, one of the things you can deduct is "state and local taxes" -- up to a maximum of $10,000.
"State and local taxes" includes:
a) income tax OR sales tax
b) plus real estate taxes
c) plus personal property taxes.
If you deduct state income tax, you can't deduct state sales tax. If you deduct sales tax, you can't deduct state income tax.
If you choose to deduct state sales tax, you can deduct the sales tax you actually paid, if you kept records, or you can deduct the "standard amount" which is an estimate provided by the IRS based on your state and your income. If you use the standard amount method, you can add tax you paid for the purchase of a vehicle, aircraft, or home, but not other purchases, even if they are large purchases.
Whether or not you should deduct sales tax or income tax, or itemize at all, depends on your total facts and circumstances. If you enter all your deductions into Turbotax, the program will choose the best option for you. If you choose to deduct sales tax and use the standard method, you can add on top the car sales tax but not the tax on the ring.
