Any size business can easily employ modern technology freely available, as I have, to calculate, collectandremit sales tax for any jurisdiction in any state.
There are some retailers, direct marketers, mail order catalogs and others that oppose the current move to allow states to require these channels to collectandremit sales tax.
New Hampshire, for example, has no sales tax, but a Granite State Web merchant would be forced to collectandremit sales taxes to all the governments that do.
If they collect the taxes and fail to remit, they can go to jail because in collecting the sales tax they are an agent of the State and failure to remit is something like embezzlement.