In a post below, commenter theogt brings up the point that when Roy Williams plays the "linebacker" position in what I was terming the nickel, that is termed by Wade Phillips in his playbook as a dime. I was referencing it as a nickel because the alignment is what is traditionally thought of as the nickel, with five defensive backs and two players lined up at the linebacker position. But Wade Phillips runs both a nickel and a dime defense out of that formation. Usually, we think of the dime as six defensive backs lined up wide and deep, with one player in the linebacker spot. Apparently, when Roy is playing there he is running the responsibilities of a dime back. I was giving the conventional sense of the term nickel, but that is not necessarily correct in Phillips' defense. Depending on the responsibilities assigned to that player, he is either what they call the XB (cross-backer) in the nickel, or the D back, meaning the dime back.
Given Wade's comments on the subject, this formation with Roy is called the dime. Although I have no idea what would happen if the offense ran four wide receivers, I guess he would have to split outside and take one in coverage.
Anyway, the point being that I was relaying the traditional sense of the nickel, but theogt correctly pointed out that Wade terms this the dime. Sorry for the confusion.