generally speaking, with regard to in-state sales, you must collect and remit sales tax on all taxable sales. . .with regard to out-of-state sales, you generally must have some sort of nexus (i.e., contact) with the other state in order to be required to collect and remit that other state's tax. . .while the threshold for contact/nexus is lower for sales tax (than for income tax), where internet-only sales (where the purchased items are shipped via a common-carrier. . .ups. . .usps. . .fed-ex) are concerned, states have had a difficult time requiring interstate vendors to collect and remit their sales tax as there is generally little or no tangible contact with those other states. . .
i have a masters degree in taxation and i have had quite a bit of multi-state tax experience over the years and my experience has been that, with internet sales by smaller companies/vendors, you will generally not be harassed by other states for sales tax purposes. . .however, you should definitely collect and remit sales tax for sales within your home state (assuming that the products you are selling are actually subject to sales tax in your home state). . .
you might want to bounce this question off of eddymerckx too. . .he's a tax attorney. . .