I suppose there is the what works for you factor and I wish I could play like Barney...

As far as I understand it there are 2 common fingerings for playing this stuff on the tenor banjo.

I use my little finger for the 7th fret and sometimes the 6th. (Fiddle/mandolin fingering I think).

Others may bring the little finger into play for the 5th fret and perhaps change position for the 7th.