Idaho charges sales tax on vehicular transactions. I took a sketchy transaction to the dmv, Nevada title, multiple owners, and I didn't chisel them on the tax.
My experience (Idaho) is, if you don't chisel them on the tax, they'll process it.
A positive attitude and the willingness to pay tax makes all the difference.
Leave tax disputes for another day. Pay up, don't try the Sportster for a hunsky dodge.