ServerPartDeals no Sales Tax?

I've been going back and forth whether I should buy used or new on (6) 18TB HDDs. I was going through the checkout process on various sites to get an idea of out the door price for (6) drives. When doing the checkout process on SPD, it did not calculate a sales tax. After calculating numbers between various sites, SPD with its already great price and no sales tax it really is a no brainer.

Why is SPD not charging sales tax?