Found a domain.com coupon code which will give you 15% when you register / transfer / renewals your domain with them.

Coupon code: "htmli.info" (yes, the coupon code is without "")

I have calculate the cost of register a new domain, it can be $7.60 for each domain or $5.95 if you register them in bulk, so I think it's perfectly for those who want to register / transfer / renewals domains as the price is low....