What is the optimal way to calculate tax: apply tax to each item, then sum the prices, or sum the prices, then apply tax? When are prices...

What is the optimal way to calculate tax: apply tax to each item, then sum
the prices, or sum the prices, then apply tax? When are prices...

What is the optimal way to calculate tax? Lets say tax is 7.5% or 0.075.
$2.32 X 1.075 = 2.494 --> Rounded: $2.50 You can say that item is $2.50
(tax included) and if you have two items: ...