Any decent rod of modern vintage should be able to comfortably throw a line a weight above or below the rod's rating. Try it out and see how it feels.
Just as important as the rod, is the flies you normally cast. If you tend to throw larger or weighted flies, the five weight line may give a bit of trouble.
The weight of the line not only carries itself, but has to turn the fly over.
I try to keep the line matched to the rod, simply because as stated by Tim A, best all around for diverse conditions.