Let's say you gained 5000 on your stocks for the year. How much does the IRS take from this. For example what if you don't have the money to pay the taxes because you haven't sold your stock shares?

If you havent sold the stock then you dont owe any taxes. You only pay taxes on realized gains. The amount of taxes depend on if its a long term gain or a short term gain. Short term, for tax purposes, is less than one year and short term gains are generally taxed at your normal tax rate. Long term ins more than a year, and what you pay depends on your tax bracket.