Disclaimer: I am not an accountant. I would figure tax holidays are optional and might even require an application to take advantage of. So you would charge the regular sales tax and remit it to the state.

UPDATE: Out of curiosity I looked it up. And it looks like sales tax holidays depend as usual on the state. The MO back to school one is optional if less than 2% of merchandise is affected. But the TN one doesn't look optional.