Minimizing sales tax?

Just for kicks I called a dealer in Oregon
(where they have no sales tax)
and asked about buying the car there
(even though my primary residence is in
California).

They told me that the attorney general has
been scrutinizing all auto sales, and that
they are required to do "due dilligence"
(to prove that you are entitled to buy
the car there) including making sure
that you own property in Oregon.

Then I checked around California where sales
taxes vary regionally
-----------------------------------------

County Tax County Tax County Tax
Name Rate Name Rate Name Rate

Alameda 8.25% Madera 7.75% San Joaquin 7.75%
Alpine 7.25% Marin 7.25% S. Luis Obispo 7.25%
Amador 7.25% Mariposa 7.25% San Mateo 8.25%
Butte 7.25% Mendocino 7.25% Santa Barbara 7.75%
Calaveras 7.25% Merced 7.25% Santa Clara 8.25%
Colusa 7.25% Modoc 7.25% Santa Cruz 8.00%
Contra Costa 8.25% Mono 7.25% Shasta 7.25%
Del Norte 7.75% Monterey 7.25% Sierra 7.25%
El Dorado 7.25% Napa 7.25% Siskiyou 7.25%
Fresno 7.75% Nevada 7.25% Solano 7.25%
Glenn 7.25% Orange 7.75% Sonoma 7.50%
Humboldt 7.25% Placer 7.25% Stanislaus 7.375%
Imperial 7.75% Plumas 7.25% Sutter 7.25%
Inyo 7.75% Riverside 7.75% Tehama 7.25%
Kern 7.25% Sacramento 7.75% Trinity 7.25%
Kings 7.25% San Benito 8.25% Tulare 7.75%
Lake 7.25% San Bernardino 7.75% Tuolumne 7.25%
Lassen 7.25% San Diego 7.75% Ventura 7.25%
Los Angeles 8.25% San Francisco 8.50% Yolo 7.25%
Yuba 7.25%
--------------------------------------------

And I found that a dealership a few miles further away from me (Marin County) is
in a 7.25% (vs 8.25%) sales tax area.
I asked them about this, and they said
that they are required to collect tax based
on the county where you will title/register
the car...

Oh well - I guess people should probably just
buy from a dealership that is local
and not worry about trying to do
anything about sales tax...