Many states have had sales taxes for a long time and have relatively effective ways to deal with this, we just need to look at them. I am sure localities like Juneau have limited ability to enforce and mechanisms to collect but it becomes a different beast at the state level.

Thanks to California and Amazon, a state can now tax sales even if the business does not have a physical presence in the state. That means we're not going to get around a sales tax by purchasing something on the internet anymore, sorry. This is a common concern local businesses bring up about sales tax but this excuse is history.

Also states levy sales tax on items purchased in other states and brought in. If it comes from a state with no sales tax you would pay the full tax; if purchased in a state with a sales tax you would pay the difference. So you're not going to buy a car in another state and bring it here to escape taxes. Could you? I suppose but you would be taking a big risk since it would be illegal.