Itīs an interesting question . But in geral lines, winrate in cash-games is given by bb/100, that is, number of bb won, every 100 hands played at the limit that you are playing, in this case, NL2.
Winrate = "Big Blinds Won" / ( "Hands Played" / 100 ).
"Big Blinds Won" = Total Gain / Big Blind limit -> in your case use $0.02
I strongly recommend you to have a tracker to do this job for you, like PokerTracker or Holdem Manager.