I think that displaying prices exclusive of tax(es) is rule rather than the exception all over the US. It's definitely the case in LA and SF. A full list of regional sales taxes for CA is available [broken link removed].
One of the reasons for this is that every city and/county can set its own tax rate. And as most almost every US will tell you if you question the pricing policy, "we don't charge you tax, we just collect it for the government."