When you apply for wholesale, we do need your sales tax ID. If you are in a state where there is no Sales Tax, lucky you. But there is a business ID most likely.
If you live in California, it is absolutely necessary that we have your Sales Tax ID, which we verify with the State. Additionally, you must sign and submit the Certification which says that you recognize that you must pay taxes on these items (through sales to your customers, or if you choose to use it, then you still owe the state sales tax). Without this, you will be charged sales tax.
If you live outside California, and in a state where sales taxes are charged, you still aren't off the hook. One day in the near future, all states will require online business to collect sales taxes. So in preparation for that wonderful day, we require your sales tax ID.
The National Retail Federation is actively lobbying for this and some major players have already acquiesced, namely Amazon.
It is a nightmare for small online stores and a national tax makes more sense than the 7,500 local tax jurisdictions and as many as 15,000 tax rates to administer. But getting the states to agree to sensible solutions has so far been futile.