Taxes when Selling stocks when the market is high

Can someone tell me what the process of paying taxes on gains looks like? Like if I were to pump and dump some a stock (probably not an ETF) that goes up wildly, and then buying back in, does Robinhood take the tax out right away payroll style or do I get the full gain out for the stock I sell? I’m increasingly becoming interested in pump and dump for some stocks. Is it a hassle?