Hi Bob, that will come down to what supply method you are using. For example, if you will be purchasing from a wholesaler, then a tax id may well be required, in fact it's pretty much the norm with any wholesaler to request a tax if before trading with you.
Surplus stock, drop shipping, a tax id isn't usually required to use these supply methods.
Of course, as for you own taxation record keeping, well that is up to you :)