I actually used to be a sales tax auditor for the state of Pennsylvania. That use tax regulation applies in PA as well. I use to tax businesses in the Phila area all the time that bought stuff in Delaware to avoid sales tax. We would also add penalty and interest. I don't want to be a bummer, but I have many friends that still work there and the days of no sales tax for online purchases may be coming to and end in the next few years (for folks in states that have sales tax).