I did the math on this a while back, and I don't remember *all *the specifics, but in a perfect power clearing situation where you get every camp almost on respawn, the max you can get from your half of the jungle is 445 seconds/100 seconds per respawn rounded down (because you don't have partial respawns) is 4 respawns (5 counting initial spawn) for minor camps, and minor camps in total give 1+3+4+2=10 Creeps per respawn, times 5 spawns is 50 CS from small camps. Add in 2 large camp spawns for another 12 CS, and the max you could get if you cleared with perfect efficiency is 62 CS (not counting lane tax, Scuttle crab, or counterjungling). In most situations, your clear isn't going to be perfectly on time (you need to back for items and sometimes gank) so I'd say 45-50 at 10 minutes factoring in lane tax, Scuttle crab, and some counterjungling would be a good goal.
At 20 minutes, probably more like 100-110 CS would be ideal, since you will have covered more lanes, and more camps will have spawned in the second 10 minutes than the first since you have to wait 115 seconds before the first spawn even happens.
End game, (between 35-45 minutes most of the time) you will probably want between about 180 and 240 CS as the jungler, but that amount varies pretty dramatically from game to game based on how much you split push, team fight, get objectives, siege, etc. so those numbers are a lot looser than the 10 and 20 minute goals.