I say, something even a person originally from US should have learned.
Otherwise, this person originally from US might be laughed-at by
persons not originally from US.

Let us analyze your $10-stuff example.

You said if 5.75%, you just add 5.75 % of $10, which is $0.58, to the
$10. So you sell the stuff at $10.58.
Ok, so sale price is $10.58.
Then taxman gets his 5.75% of $10.58.
0.0575 times $10.58 = $ 0.61
$10.58 minus $0.61 = $9.97
Hey, that is not $10, after tax!

Suppose we follow this former foreigner.
Sale = $10.61
Tax = 0.0575 times $10.61 = $0.61
After tax, $10.61 minus $0.61 = $10
Hey,....
Zeez, is there magic in what the guy learned from outside the US?

Hardly. The guy just learned Math as Math is learned in and out of the
US.

It is Accounting, maybe.
But it is just Algebra. Algebra anywhere.

----------
You want a crazier formula?

Say, you have a product that worth "x".
You know the sale tax is "t" percent.
You want add "y" to "x" so that the selling price is (x+y).
How much should this additinal "y" be so that, after tax, you'd end up
exactly with "x" from this product.

Sale price = x+y
Tax = (x+y)*t
Net = Sale minus tax = (x+y) -(x+y)t = (x+y)(1-t)

Net = x, so,
(x+y)(1-t) = x
(x+y) = x/(1-t)
y = x/(1-t) -x
y = x[1/(1-t) -1]
y = x[(1 -1(1-t))/(1-t)]
y = x[t/(1-t)] ---the formula.

Note: t is in decimals.
So if the sale tax is 5.75%, then t = 0.0575

Apply this crazier formula to your $10 example.
x = $10
t = 0.575
y = 10[(0.0575)/(1 -0.0575)]
y = 10[(0.0575)/(0.9425)]
y = 10[0.061]
y = $0.61 -----***

Meaning, you really need to sell the product at $10.61 (not at $10.58)
if you want a net of $10 after tax.

--------
By the way, if you want to add 28% to $100, you will really end up with
$128.

Nobody anywhere will say "No way".

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