It's not enough to purchase the goods intending resale; you must also be registered as a reseller.
In fact, if you can't provide a reseller's certificate (or license, the exact term depends on the state) then the seller generally must collect a sales tax on the sale.
Correct.. and it's in that specific circumstance: where you are licensed, and for whatever reason the retailer charged you sales tax anyway on an item for resale... then you can file with the state to receive that money back. My point was that there's no reason any retailer or manufacturer would pay sales tax on the inputs for their goods.
In fact, if you can't provide a reseller's certificate (or license, the exact term depends on the state) then the seller generally must collect a sales tax on the sale.