Following are the steps to highlight and delete all the tax rates rows in WooCommerce.

Method one: (Assuming that you are at your WooCommerce “Standard Rate” Section)

1. Press and hold the “CTRL” key
2. Click to highlight all the rows then release the CTRL key
3. Click the “Remove selected row(s)” button
4. Click “Save changes” button.
5. Upload the new table.

Method two:  (This method clear all the tax rates at once)

1. WooCommerce->System Status menu and then click on the “Tools” tab.
2. Click the button labeled “Delete ALL Tax Rates”.
3. Click the button labeled “Clear Transients” .