sales tax on freerunners

[Robin Paulson]

while i was looking up the gst/duty i'll have to pay for importing my
freerunner, this occurred to me - is american/californian/whatever
sales tax included already in the price of the phone? will i be taxed
twice, or will your local tax only be applied for local purchases?

this might seem like a dumb question, but i've bought plenty of stuff
from another country where the seller included tax even though it's
being shipped abroad