There are some pretty severe penalties for accepting bribes in basically any aspect of life in the United States and I could see officials shying away from that even if they were approached by criminal organizations to intentionally tamper with game outcomes. I guess they could take money to keep a game closer than it otherwise might be, but that's risky business.

What I think does go on (or at least goes on more often) is that personal bias plays a pretty big role in how some officials call the games. Refs are very aware of how to preserve their own livelihoods. So in this game, Wisconsin has been a big name in college basketball for a long time and they're in the B1G. Given the sheer volume of seeds the NCAA committee heaped upon the SEC and B1G teams this season I suspect the officiating crews know where their bread is going to get buttered and that can impact their decision making during a game. I don't think any officials that want to earn the best money for their time would want to get on the bad side of either of those two leagues right now.