The sales tax you have to pay is depended on where do you live; in essence, taxes are calculated based the county or City, which you live in. For Example, if the individual that’s buying the car lives in the City or County of Philadelphia, the sale tax is 8% of the buying price of the vehicles. If you live in Bucks, Montgomery, Delaware and other counties within the Commonwealth, the sale tax rate on the purchase of a vehicle is 6%.