AppleTV 3 wakes iMac every 10 minutes
After Apple TV Software Update 5.1, I comfirmed this issue was resolved.
Try to update your FW!

The following my old comment is for old FW. I leave it just for knowledge.

I had have same problems. I know Snow Leopard's mDNSresponder wakes a Mac every 2 hours during sleep. So a similar thing occurs on AppleTV every 10 minutes, I guess. 

In my case, AppleTV woke my Mac If I set Home Sharing on it. So, 1st option is disabling HomeSharing.

However, I didn't want to do that. So now I avoided this to kill iTunes before Mac sleep. This means it doesn't register Home Sharing service for sleep proxy.

Note: 
 1. You have to wake up your Mac by some method(http, ssh, magic packet or something) when you want to use your Home Sharing.
 2. You cannot use sleepWatcher to make 2nd option because it's too late for killing iTunes after sleep trigger. So you must check IDLE time and sleep timer.