It's hard to say for sure. Sometimes the manga keeps going and sometimes it doesn't. You could look up reviews or ask manga enthusiasts to find out if Nana's manga continues after the anime.
The Nana anime wraps up earlier than the manga. The manga continues to unfold with more complex and in-depth storylines that weren't included in the anime adaptation. It's kind of a bummer for fans who wanted a complete visual adaptation.
The Nana anime doesn't exactly match up with a specific point in the manga. It kind of stops prematurely, leaving out some crucial plotlines from the manga.