It remains a felony offense no matter the denomination of the bill. Alabama law, as I've just read, calls possession of a forged instrument (even in the third degree) a class D felony.
The purpose of the thread about pennies is all about convenience. For example, the hospitality tax is two percent. Instead of $1.02 for the final total, charge .98 for the item and it's a buck.
I got into the bar business in the mid '00's and got out of it just a few years ago. In all of that time we saw one counterfeit bill. (He had dumb MF written across his forehead walking in the door.) On the other hand, a friend of mine that owned an ACE saw them enough; they always checked the $20's.