[Nexus 7 (2013) General] sfhub:
We don't have a nationwide VAT (like European countires) for consumer goods so sales tax is left to the individual states and local govt to determine.

There are 5 states with no sales tax, Oregon, Delaware, New Hampshire, Montana, and Alaska. Sales tax ranges from 0% to 13.725%. Most major cities/states are in the 8-10% range. Most other states are in the 5-7% ranges. Basically the state determines the sales tax and whether the counties/cities within the state can charge their own add-on tax. If the latter is true, counties/cities within the state will tack on their own sales tax to the state sales tax. Usually the county and/or city tax (if it exists) is around 1-2%. That is why a County like Los Angeles will have a 9% sales tax which happens to be what is charged in the City of Los Angeles, but other cities, also in Los Angeles County like city of Santa Monica will charge 9.5%. I believe the minimum California state sales tax is 7.5%

It used to be that sales tax for internet sales was determined by the company's nexus (ie which states they are doing business in) If a company had no nexus in the state the product is being delivered to, they didn't need to charge sales tax.

This is changing though because many states have budget issues and lobbying groups from the major local retailers like walmart, target, etc. want to level the playing field (since major retailers have nexus in almost every state, they need to charge sales tax for their online and local sales)

States are finding creative ways to forces companies with no nexus in a state to charge sales tax. Amazon used to not charge sales tax for any state except Washington (their HQ) and possibly the states they keep distribution centers in (though I'm not sure of the latter). Now they are forced to charge sales tax in CA and NY, and possibly other (but not all) states. However, this is a special agreement between Amazon and state of California and New York. Other Internet retailers might not be collecting state sales tax because they are still in the Internet sales tax exempt if no nexus situation.

Besides the sales tax, some states have an E-waste (eletronic waste) additional flat tax/fee on electronic items (purportedly to pay for waste cleanup/recycling of toxic electronic) In CA this fee is $3 per item. We also have various tourism and specialized taxes that apply to specific categories, like hotels, airline tickets, car rentals, etc. Then we have special "surcharges" that companies are not required to collect for the state, but they tack on anyway to defray costs they incur. The latter 2 don't apply to consumer goods, but you'll see them if you visit the States.

Many times sales taxes can add up to 8-12% on an item like a $200 Nexus 7 in many of the larger states/cities.

Also our prices are always listed without sales tax. We do not find out the sales tax that is being charged until we checkout (and/or enter the place where the item is being delivered in the case of internet sales) This is not law, but rather a matter of practicality. They pretty much expect people to know their local sales tax rates, but for Internet sales, the rules are too complex for individuals to figure out and they don't know the rate until you enter the zip code (postal code for where product is being delivered)

I'll leave it up to you to determine whether the taxes are significant enough to purchase from one state vs another.