The promotion is still available but US$10.- more only.
http://www.amazon.com/Garmin-Forerunner-405CX-Sport-Monitor/dp/B0025UHKNS/ref=sr_1_1?ie=UTF8&qid=1322726079&sr=8-1
The states law mention that the sales tax only apply to the order within the same state. Any order outside the company home base "state" can't claim for the sales tax.