$4.95 per trade up to 1000 shares, $0.00495 after is not cheap. That is $9.90 per round trip trade. If you trading penny stocks, then chances are that you will be purchasing more than a thousand shares.
Example
CYCC:US $0.67/share. 1000 * $0.67/share = $670. $9.90/$670 = 1.47%.
This means that you have to make 1.47% to break even before you make any money. Even if the transaction was worth $10,000, it would take 0.1% to break even. Those percentage points add up quickly, and I would prefer them to go towards my balance and not to the broker.
@cashclay, I would be sure to look at the charges very closely.