Does cancelling your credit cards affect your credit rating?

I just applied and got a sears master card because it gave $10 off of my first purchase. But I have no real need for it as I already have a visa. It is a no annual fee credit card, so my question is does cancelling it right away or within a month have any negative consequences? Ie. bad credit rating etc.

Thanks 

Signing up:
You reduced the average age of accouts > Lower score
You added a recent credit file inquiry > Lower score
You decreased your percentage utilization > Higher score

Cancelling:
Would increase your average of accounts > Higher score
Would decrease your percentage utilization > Lower score
Doesn't change the fact that you had a recent inquiry > No effect relative to the current situation

Overall, if you cancel, you will be in a slightly worse position than you were at before you signed up. But it is quite marginal and will heal itself after some months. My advice is to just cancel it if you don't need it.