how are tax exempts handled

[eburtonlab]

Users that can document a state sales tax exemption can provide that documentation to eBay to be made exempt from state sales tax for future purchases in the account shipped to that state.

If users also need to make some non-exempt purchases, that would require a second account or a purchase as a guest.

https://www.ebay.com/help/buying/paying-items/paying-tax-ebay-purchases.html?id=4771#section2

[woodland_gnome]

If you mean you are exempt from sales tax by your state as a buyer, you file your papers with eBay, see   https://www.ebay.com/help/buying/paying-items/paying-tax-ebay-purchases?id=4771&st=12&pos=2&query=Pa...

Once you are registered be sure to not buy anything that does not fall under your exemption using the account you registered for.  You would need a separate account for non-exempt purchases.