As I understand the law in North Carolina and several other states...
If you buy something from a North Carolina merchant and pick it up here in NC, the merchant is required to collect and remit sales tax. It does not matter where you live nor where you plan take the item.
If you purchase the item from a Tennessee merchant for instance, and have it delivered by the merchant to, North Carolina, the merchant is technically doing business in NC and is required to collect and remit NC sales tax.
If you purchased the item from the TN merchant by mail, internet, phone, etc., and had the item delivered to NC by a 3rd party such as UPS or Yellow Freight, the merchant is not required to collect tax. However, this case requires you to self report this purchase and pay the NC sales tax. Granted, almost never done but it's the law...
If you buy an item from an individual, he is required to collect and remit the sales tax or you are responsible for reporting and paying. Again, the law...
There is a line on the NC state tax return for owed sales taxes on out of state purchases, purchases from individuals or any other case where the state did not get their cut.
If anyone collects taxes and doesn't remit them to the state, the state gets really upset!