It depends. As long as there is a paper trail (checks) there isn't a problem. It is when the transactions turn into cash that there is a potential problem and reporting requirement. And there aren't enough facts here.
Did the person passing out the cash know (or should they have known) that despite the separate entities shown on the face of the checks, they were fronts for a single person or entity? Did the same person present all of the checks so as to put someone on notice?
Look, you have a small business that grosses about 5 million a year. All that revenue comes in by the way of checks through the mail. Most is deposited in the bank except maybe 20% that is cashed locally at one of these check cashing stores. Most of that is used for daily operating expenses for the drivers and other pressing matters. What I am saying is these check cashing places can go through a lot of cash in a weeks time.