5-6PTBB/100 over 100k hands.
3PTBB/100 over 100k hands for full ring.
It might be worth clarifying, for those not using Poker Tracker and since Paul's original question just stated BB/100...
PTBB = PokerTracker Big BETS (ie. 2 x Big Blind in Limit poker). There is an option, on the Preferences tab, to have PT treat BB as Big Blinds if you only play NL.
So, 5-6 PTBB/100 = 10-12 Big Blinds/100 or $5-$6/100 at 25c/50c (50NL).