Quote from Wikipedia:

Since January 2017, 5 states (Alaska, Delaware, Montana, New Hampshire and Oregon) do not levy a statewide sales tax,[1] while California has the highest state sales tax with a base rate of 7.25%. (The territory of Puerto Rico has a higher 10.5% value added tax since April 2016).[2][3] In some states such as California, counties and cities impose additional sales taxes, and total sales taxes can be over 11%.

If you sell anything in Nevada at the Convention, you are required to collect Nevada sales tax and remit it to the Club who is sponsoring the Convention.

If you sell on the internet (e.g., eBay) you may be required to collect state-sales-tax and remit it to the state your buyer lives in. If you don't, the buyer in most cases has to remit a Use tax to his state. Almost nobody does this right now. The law may change, or ebay may change its rules.

If you sell on ebay and live in a state that has no state sales tax, there's no current law that requires you to collect a the buyer's state tax and remit it. This is the issue that federal courts are debating currently. I suspect it will be ruled un-constitutional if it is ruled otherwise.

If you live in a state (like Oregon) that has no state sales tax and travel to a state with a state sales tax, you don't have to pay sales tax on your purchase there. Many stores say you must have a certificate from your state that says you are a dealer exempt from collecting your state's sales tax. Many states don't have this rule for their dealers, particularly if you are traveling to a nearby state. I have been unable to get a certificate from Oregon saying I am a dealer and don't have to collect anybody's sales tax. If you have, please email me with the process you've successfully used.