Using the chart, at least here in NY is a safe harbor so they can't audit your online purchases.  It is a sales and use tax so you have more purchases than you might think.  Ever go on a trip and buy a souvenir that you bring home with you?  Most people in NJ travel to NY a lot and do a lot of spending in NY.

When the first IKEA opened in NJ, NY sales tax people sat in the parking lot and noted NY plates with purchases.  They all received a nice little letter in the mail.