There is no such thing as a "major purchase" and I hate that Turbotax uses this terminology.
IF you are using the sales tax deduction with the standard amount method, you can add to the standard amount, sales tax paid for the purchase of a motor vehicle, airplane, or a home or major improvements to a home. Those are the only "major purchases" that count.
Yes, if you finance the car, you can still claim the entire sales tax amount in the year you bought the car. You do not spread the sales tax out over time.
