Either way, banks do not sell certified checks for cash; in the absence of a cash purchase, there would be no BSA record retention requirement.
One of the better definitions I found of a "certified check" follows. The key thing to understand is that the item starts out life as a check written by the customer, not the bank.
A certified check is the written acceptance for a specific check (essentially an acknowledgment), by the Bank, that the Bank's Customer's signature on that check (1) is genuine and (2) there are sufficient funds in the Customer's account to honor the check when it is properly presented for payment. The check is signed by both the Customer and the Bank.
Ten percent of life is what happens to you. The other 90 percent is what you do about it. Lou Holtz