CritterCoin does a few things every time a round ends.
If your school is using Houses, CritterCoin will send digital Critters to every student in the winning House. CritterCoin will send out emails to the winning students if they have a valid email on file. CritterCoin will also reset the house points of all houses to zero.
Additionally, for data collection and reporting features, each round starts a new data collection time period.