Some of this may be governed by sales tax reciprocity agreements between states. In 2010 when we bought our rig in Indiana, there was no reciprocity agreement between Indiana and Texas. We told the dealer we were titling in Texas and they did not collect any sales tax. It was our responsibility to pay the sales tax when filing for the Texas title.
We were lucky that we got home 19 days later. I called the tax office on day 20 and discovered there was a 21 day rule, after which we would have a 10% late payment penalty added to the bill. Saved several hundred dollars by getting there the next day.
Of course things may have changed since 2010. And I've been reading about a tax bill under consideration in Indiana so dealers don't have to collect sales tax.