Do Atlantic City casinos shuffle after every round of Blackjack?

Can't tell you much about Atlantic City, but in Las Vegas the answer is "it depends". Each casino owner has his own ideas on what is fair vs what is convienient, so you will find some tables with a machine that shuffles 4-6 decks at the same time you are playing out of one shoe, then when the shoe is empty, all six decks are moved tot he shoe, and the discarded cards are moved to the shuffler. But you will also find the insideous CSM (Continuous shuffle machine) that shuffles all the cards after each hand. It speeds up play, but makes the dealer's life a bore, and makes counting purely impossible.