Pennsylvania plans to begin collecting sales tax on all internet purchases, including those made at, beginning Sept. 1, according to the The Journal of Commerce. The law was supposed to take effect beginning Feb. 1, but collection was postponed until September after online retailers complained that they needed more time to adjust their accounting systems.

Since a 1992 Supreme Court ruling banned sales tax from being collected on goods shipped from a company without a retail presence in the recipient's state, Americans have become accustomed to not paying taxes on interstate online purchases.

But maybe not for long. Pennsylvania is not alone in trying to recoup missed internet sales tax revenue, which totaled $345 million last year for the state--California legislators have also tried to wring much-needed revenues from the online retailing giant, and eventually prevailed, with Amazon's California tax bill coming due starting Sept. 2012.

The push to collect sales taxes from Amazon does, however, have a silver lining: it will allow the retailer to open brick and mortar stores without tax consequences. In the past, opening a store in a state would trigger sales taxes to be collected on all orders from that state, but if Amazon customers are already paying sales taxes, this penalty no longer applies.

The retailer may begin testing the waters in Seattle, where it's rumored to be opening a small store. It would be following in the mold of Apple, which after decades of online-only retailing, has become a formidable presence in the brick-and-mortar retailing market.