Every state I have lived in charges sales tax on the purchase price whenever you register it. Buying out of state only makes the process more complicated, not cheaper tax wise. That said, it's amazing how many people here in Omaha have cars registered in South Dakota(PO Box I guess) where the tax rate is lower and where they charge $50 a year for plates instead of hitting you with a personal property tax every year based on the value of the vehicle. My '09 35d was over $900 for the plates alone. Plus sales tax. Nebraska will even pay you a bounty($200 I think) if you turn your neighbor in for out of state plates. When I moved here from PA, I waited almost 2 years to register my old car here. The post office was nice enough to forward me my renewal notice 6 months after I moved.

If you pick it up at the performance center, you have to provide temp plates or they will not let you leave.