SD has no sales tax on vehicles you register there. They do however have an excise tax that was just raised from 3% to 4%. You will have to pay this to SD. Do not pay any sales tax to the state you purchase it in. I bought my 2014 Ram dually in Washington state last year and the dealer had NO idea! He tried to collect sales tax so I started walking out. He instead collected ONLY the temporary tag fee and I took care of the 3% excise tax with SD myself.