As WyoTraveller alluded to, for vehicles purchased in one state and registered in another, you typically won't pay the sales and use tax in the purchase state. Many (most?) states offer a transit permit or similar temporary registration for that precise situation. (Massachusetts is a big exception; they neither offer transit permits to out of state buyers, nor recognize those of other states for buyers who are Massachusetts residents. They do grudgingly allow those of us residing the other states to travel through with temporary plates en route to our home state.)
If you're transferring plates from a previous vehicle, some states let you move the plates physically to the new vehicle and then do the paperwork a few days later. That can avoid the (usually nominal) transit permit fee when it's an option.
Laws do vary in their specifics, so it's worthwhile to check with the states involved. But I'm not aware of any state that requires out-of-state buyers to pay sales and use tax on vehicle purchases. This is technically a use tax, not a sales tax, charged on the use of the vehicle in the state. (If it were an actual sales tax, their own residents buying vehicles in other states would not have to pay it.)