Another thing to consider is that many wholesalers and suppliers require a sales tax resellers certificate to validate a business but if the items are purchased from out of state, they aren't on a resellers certificate because the resellers certificate is only for purchases from within the same state. Therefore, it is taxable because it's an out of state purchase, not because it's on a resellers certificate. This is a common reporting error on the tax form. I'm not saying the OP purchased it from out of state, just adding a little info here.
Bob