You don't pay sales tax in the state or country you buy it from.
You pay sales tax in the state or country you register it in.
I bought a boat in Wisconsin. I only paid the guy I bought it from.
I paid tax at home.
I sold a boat to a Canadian.
He got hassled at the border and then paid tax at home.
But I want to say that he had to pay two different taxes.
Maybe one crossing the border and one registering it.
Be aware that the Wisconsin trailer will not have a license plate or registration.