I have already been paying sales tax on some sales (Michigan to Michigan transactions). The tax is added to the buyer's bill.

The recent Supreme Court ruling overturns prior precedent and says that a state can charge sales tax to sellers who sell to customers in the state even if the seller does not have a physical presence (i.e., a store or warehouse) in that state.

Three states have adopted new laws to take advantage of the ruling. Other states can fully adopt it, or they can adopt some variation that might not encompass small-time sellers. But once they have Ebay collecting the tax, states have little incentive to let Ebay sellers out of the trap.

Ebay has said they will collect and send the sales tax to each state without imposing a fee on sellers. Sales tax will not be subject to the 10% commission like shipping is (there are huge complications if a seller tries to add a service charge onto a sales tax, and a commission charged by Ebay might lead sellers to add a fee just like many of us add something to shipping to cover the 10% commission). Of course, all rules are subject to change, and profit is a big motivation to change things.