The 5c rule is just for Direct+. For example if the offer is 6c away from the last price you can not NX it.
The rules do not matter. The only thing that really matters is how much the specialist is making off you. If he wants to fill you even though the rules says he can't, you'll get filled. How many people have gotten short on a downtick that turned out to be a bottom?
You've told me in a PM that you use NX a lot and those are the best possible fills. How could you not know about the 5 cent rule?
I use NX dozens of times a day and myself, along with all of the successful NYSE traders I've asked, have no idea about any 5 cent rule. Nobody on this thread has been able to explain exactly what the rule is, except that it's only applicable to Direct X users, which I am not.
5 cent rule is simple. If its not Direct+ then it is DOT. If it is DOT then you don't get the electronic fill but a "DOT" fill.