We are CA residents and bought our first mh in AZ. We had to pay the AZ sales tax and was told that since the CA tax was less, that when we registered the mh in CA, CA DMV would refund us the difference.... never happened...lost about a grand on that deal. However, the sales tax was included in the loan.
Our 2nd mh was purchased in OR and they calculated the sales tax (and registration fees) for our place of residence in CA (state/county) and also included both in the loan.
So, it seems it depends upon the state of purchase.
Ron