Maybe it's just this boomer, but I would NEVER deposit cash into an ATM. What happens if the ATM makes a mistake (happens all the time with withdrawals where people don't get the cash)? There is no such problem when a human teller counts the cash and generates a receipt.

As for the SARs, I always make a side comment when I am depositing cash, usually along the lines of "garage sale" "girl scout cookes" "graduation gifts for my kid" or even "sold my vehicle" (when depositing $9k). AFAIK this has successfully headed off any SAR filings. Of course YMMV, depending on how you present yourself and your prior account history. Personally I think the better course would be to deposit in your account and then pay the bill.