Only $20? That actually seems quite reasonable for being caught avoiding taxes. In theory, it should be possible to declare and pay VAT in advance, but I have never figured out how.

Anyway, the penalty used to be much more. I've payed over 300dkk on a 100dkk item years ago.

Amazon.com offers to take care of import taxes for you, and many of the dodgy Chinese sites offers tax-insurance.