You don't have to pay taxes for mine cryptocurrencies. Only if you sell them for fiat money.
As long as ou keep the coins and use them to buy directly with them, 0 taxes are paid.
You're wrong.
In IRS Notice 2014-21, bitcoin mining is considered income on the date of receipt. You need to work out the number of mined coins * the daily price. and declare it as income. You will pay taxes on that income like any other income.