Legal Question in Business Law in New Hampshire

You don't. Unless you have a "nexus" in a state, you have no obligation to collect and remit its sales taxes. This means having some physical presence, not just a virtual Web presence. Hungry revenue authorities have been trying to change this for a long time, but until or unless Congress changes the federal law they are unable to chase online retailers. Technically, the buyer is obliged to pay "use tax" (same amount as sales tax, but imposed upon the buyer when no sales tax is collected), but of course hardly anyone is aware of the obligation or complies even if aware.

Best wishes,

LDWG