Because it is hard to see from the camera how many coins are there in particular piggy bank, there are working small permoniks (aka miners) with funny caps.
Permonik randomly wanders the room and re-counts the coins in piggy banks. Always he erases an old number and writes his count on the piggy bank with marker.
The robot watches permoniks. He sees how fast they are and if they count well (their counting is equal the majority of other permoniks for given piggy bank). The lottery rewards fast and honest permoniks with higher odds of win.
There is one more thing. When doing transaction, you may leave a small number of coins (aka the fee) under the piggy bank. This is a reward for permonik as he visits the piggy bank for recounting.
Each permonik has a master and all his revenues go to master's piggy bank.
Every 10 minutes some coins are dropped in a big dark pool and everyone interested in catching them play hungry hungry hippos until some lucky person gets it.
