Suspicious transactions are usually money laundering.
Although not illegal a bank will have to report any transactions of $10,000.00 or more that occur too close together.
If you're a bank and someone is making $10,000.00 deposits everyday or every few days then that could be suspicious because unless you're rich and making that amount of money per day legally then it has to be coming from somewhere illegal.
You won't get into trouble if you do make a $10,000.00 deposit everyday or every week unless you got the money illegally or are involved in Gambling or Money Laundering.