[Your Nightmare]

Separately, it is trivial to calculate the tax using either method. Sorry you have trouble.

Really. Maybe you would like to show me the calculation for the tax on a $99.44 item using the 23% tax inclusive rate. Using the 29.87% exclusive rate it's:

99.44 x .2987 = $29.70

Let's see your calculations.

[Principled]

Let's see your calculations

99.44*1.2987

There it is. Trivial. 1.2987 IS 1+23/77. No worries.