That is what started all this, amazon has various warehouses in different states, your inventory is held there - the state then said that is nexus for you, even though it is an amazon warehouse.
I am sure there is going to be a lot of "get around this" information on the net, the question is ... will you take the chance, is it worth it
New law is simple to understand - you will collect sales tax based on destination if it is out side your state, inside your state then your state rules apply.
As this leaks down to the little guy, a couple of years away I think (not counting what the major marketplaces do) sales from your own web site will start to comply too. It is going to be easy for states to find you, almost no one anymore sends or takes a check in the mail, and all that computer data is there for the asking.
open a tab, enter this in the url
and in another tab log into facebook
go to facebook.com/settings
at the very bottom download your activity
That is the easy stuff, You wouldn't believe what the alphabet agencies have.