I bought mine in the Dallas area and I think the sales tax WOULD HAVE BEEN 8%. I did not pay theirs since I am from New Mexico. Ours is only 3 percent.
If you want a super deal on a Ridgeline tho, go to Bankstonhonda.com and look for the internet manager. His first initial is S. I don't think we are allowed to say names so won't say anymore but if you need more info email me off group (clarke@taosnet.com) and I will give you all the info. They treated me great and a super price - $500 over factory invoice - and no add ons at all but then mine was just off the transport. They usually put a "pro" package on - rear mud flaps, locking nuts, etc. I saved over $2,700 on my RTL w/moonroof.
Just call the MVD and ask them - its usually the same state wide as it is state controlled.
Mine was the one that got hailed on in Amarillo so that hurt but just got back from a 2,400 mile trip from Taos to Salt Lake to Eastern Montana and back to Taos through Denver. It was over 95 the whole way and lots of it was at 100 degrees. The truck ran great but when you drive F-A-S-T gas mileage sucks big time
Hope this helps.