To set your store’s Tax rules, you previously would’ve gone to Settings ->Payment ->Tax Manager to set your tax rates as needed.
In the new admin, we’ve streamlined the navigation slightly. You will now go to Settings ->Payment to see your store’s payment options. Once there, you’ll see an area labeled “Tax Manager” with as “Setup Tax” button displayed underneath.
Clicking on that button will take you to the tax manager with the same functionality as before. (Albeit with an updated look)