You are supposed to claim sales on your taxes you do not have to have a sales Tax ID to sale however if you reach a certain amount you do I believe it is $2400 a year but not sure.
by law however in the USA if you sell to someone in the same state you reside in then you are supposed to charge sales tax also if you purchase your items in the same state the seller is required to have a copy of your sales tax ID not to charge you Tax