You can do the live chat with them during normal business hours to ask. If you check out their Other Fees page, you will see the low priced stocks on the bottom which is as follows:
Low Priced Stocks
For stocks priced less than $1.00, add $0.003 per share for the entire order. Maximum commission per order not to exceed $5.50, with a minimum commission of $2.50.
I confirmed multiple times with them since I'm with Sharebuilder and they gouge low priced shares by taking 15% of all trades, so it was like music to my ears haha.