My company has the same thing. Ours is a 7% discount, which
almost covers the tax.
Discounts on Apple products are few & far between, but I honestly feel they are worth the price. I also highly recommend getting the AppleCare extended warranty. We got a 3-year warranty on our MacBook Pro, which I think was about $300, but it covers everything. We've gotten a new battery, 2 new AC adapter cords, had a stuck CD removed from the CD drive, and a broken key replaced on the keyboard - all for no additional cost, no questions asked. They've also given me new headphones for my iPod when I've been in for the MacBook, when I couldn't even find the warranty information for the iPod. Apple has great customer service, IMO.