TOR is the default recommended way to use xmr.to

From the FAQ:

Yes, we do [log IP addresses]. This is partially because it helps for support and maintenance, and partially because it's a royal pain to ensure that they are purged from all server logs everywhere.

It is, in fact, irrelevant whether or not we chose to log IPs. Our hosting service may anyway be logging our traffic, and their logging policy is not in our control. (This is where all the "anonymous" VPN providers lie to you…)

In summary: use TOR or I2P to be fully anonymous.