As an online seller, you will be responsible to collect and fill taxes for each state that you made a sale in.
The bill is more likely to pass: On the Amendment S.Amdt. 656 to S.Amdt. 578 to S.Con.Res. 8 (No short title on file) -- GovTrack.us
eBay is trying to fight this bill, and asking every online seller to take an action :
Internet Sales Tax | eBay Inc. Main Street
I am no longer an online seller, but I can see how can this bill effect online sellers. You will be responsible for collecting out of state taxes as multi million dollar corporation which is a lot of burden for an online sellers.
If your senate is voting Yes, send a petition, it is not yet too late to take an action.