All the exchanges regulated by the USA supposed to report each and every user's trade records, so yes you need to pay for each trade no matter its crypto to crypto or crypto to fiat. Calculating and reporting the tax can be a nightmare for a day trader so you have to find someone who is professional in that and keep all those records as per the laws.

Long term gains has less tax rates than short term so its always good to have long-term gains so you can save 30-40% from your tax.