I am an out-of-state dealer with no physical presence in Tennessee. My sales to customers in Tennessee are exclusively wholesale sales. Do I have to register for sales and use tax purposes, if my wholesale sales exceed the threshold?

No.  To apply the $500,000 ($100,000 beginning October 1, 2020) threshold, you include retail sales to individuals, businesses, organizations, and any other purchaser, whether the sale is taxable or exempt. However, you should exclude sales to another dealer for resale. Because all of your sales are wholesale sales, you are not required to register.