Tune a banjo? It can't be done....

No, seriously, I'm sure I've seen old-time style players tuned up a whole tone from double-C which makes perfect sense if you're only ever playing in D (or maybe A and variations thereof). And it sounds really nice and bright.

Banjo strings tend to be under lower tension than other instruments, so you can probably tune upwards a bit more than you could on a guitar.

The nature of a five-string banjo makes capos a bit more problematic, seeing as you need a separate 5th string capo (or something else ). If you're using lots of different tunings you might just find it just as easy to tune up.