I know a thing or two about day trading. Basically you buy 5,000 shares of a penny stock (say, a stock that's selling @ $0.20 per share) and you sell it when it goes up one or two pennies. That's 5,000 pennies, or $50. Doesn't seem like much but if you sit in front of your computer all day it adds up.
But the thing about day trading is that you can't buy more than $10,000 of a penny stock, or make a profit that exceeds $10,000. So if you buy $11,000 of a penny stock the IRS will take all of your money over the computer. The money will just disappear from your account. Or even if you buy $9,500 of a penny stock and you gross $10,001 the IRS will take all of it.
The secret to trading penny stocks is to keep everything under $10,000, including the profit.