Sales Tax is usually paid to the state the car is registered in. I purchased my car in NY and paid CT sales tax. I hear that Oregon has no sales tax....
It even varies in New York -- I paid 7.35% in Westchester...city residents pay higher, I believe it's up to 8.5% now - Yonkers has yet another tax rate, and that's in Westchester...
In CA, the sales tax is based on the rate in your city where your residence is. For example, if you live in Ventura, the rate is 7.25%. So even if you purchase the car in Los Angeles where the rate is 8.25%, your sales tax is "only" 7.25%, not 8.25.