Penny guy, in MI you need a sales tax license to collect sales tax. Unless you have a business that is more or less permanent, ie that is your livelyhood, most people do not get one. You most likely will not ever pay sales tax at a garage sale, flea market etc. Now if one of the people at the flea market is a full time dealer, than that is another story.
I believe there is something in the works for a seller on
ebay, if you exceed a certain dollar amount in sales than you are considered a dealer and are then required to obtain a sales tax license, collect sales tax and remit to the state on a quarterly basis.