Beginning on October 1st, Wisconsin will begin collecting a 5% sales taxes on Internet downloads of music, games, books, ring tones and other video entertainment. The District of Columbia and 15 states have similar laws.
From JS Online:

[Governor] Doyle has been fighting for the change for years. He and other state officials say it is a matter of fairness: Internet vendors shouldn't have a tax-exempt advantage over Wisconsin's brick-and-mortar retail stores....

Some digital downloaders don't see it that way, however.