If "close enough" works, then it's nice to have the skill. Having the skill requires occasionally using it.

Where accuracy is important, since we almost always have a calculator with us now, that's a no-brainer.

Maybe more to the point, though, understanding how percentages work is wise. It's one of the few arithmetic topics that we encounter regularly in life.

In this case, 23% of 53 and 53% of 23 each have their own little trick, depending whether you'd rather overestimate a little with 1/4 of 52 or underestimate a little with half of 24. I find it handy to be able to think that way, especially for example when trying to get out of a taxi and paying cash.

May as well just get out the calculator app to make sure

Calculator apps get order of operations questions wrong because of programmers who were too lazy to check they had their Maths correct

My point with those numbers is to just use a calculator.

My point is avoid calculator apps like the plague. Use name brands like Sharp or Casio.

Why 2nd guess anything?

Guess what the programmer of your calculator app did 😂