5% max $3 has been the standard on major online sites basically since their inception.
At the micro stakes (1c/2c - 25c/50c), the $3 cap is a pretty big deal. The games are still beatable, but with a $3 cap at 25cl50c, it would be like having a $12 cap on live $1/$2, or a $30 cap in live $2/$5. And that is obviously a lot.
@Legend5555 is right, 5% up to $3 this has been the standard rake for online as long as I can remember. To compare, "live" rake is frequently 10% up to $4 or $5 in Vegas (where you can find several rooms in a close area), and I have seen it as high as $7 or $8 cap in rooms I have played California and Illinois. (And as high as $15 on a cruise ship
.)
The live rooms here in Minnesota are 10% up to $4 plus a $2 promotion drop (jackpots, high hand, etc...). Mid stakes limit games (6/12 and 8/16 hold'em) are 5% up to 4. High limit 20/40 and 40/80 games pay a time charge ($10 per half hour) instead of a rake. (Similar time charge games at the Bellagio are only $7 per half hour.)
All that said, it's worth mentioning that online rooms often rake precisely to the penny, whereas live rooms will round down to the dollar. That does make the 5% online actually a bit higher than it would otherwise seem.
Being aware of what amount triggers the "cap" is important, because every dollar that goes in the pot beyond that is essentially "rake free." At 5% up to $3, the cap is triggered at $60. (Given $3 is 5% of $60.) Not as many 25-50c pots will reach that threshold so you usually will be paying a full 5% on most pots won at that stake. However, many 1-2 pots however will reach double that. Paying $3 on $120 pot lowers the rake to around 2%. So it's to your advantage to play higher if possible in games where the rake is capped.
To the broader question, I think 5% is surely beatable, even at 25c-50c. But the higher you can play, the less effect the rake has.