I came across these articles a little while ago.
http://www.smarteranalyst.com/2015/03/24/slowly-making-cash-illegal/
tl;dr The Feds "request" that banks call LE directly for deposits and withdrawals in the amount of $5000 or more, not just file a SAR report.
They rarely if ever file them tho, especially SARs, I work at a credit union and deposits of 2k-5k are so common place.
Banks may be different but my guess is that they get even more cash deposits then we do, and that's because they offer business accounts and are typically larger institutions. I would think you would need to be extremely reckless to attract attention.