Common core

[Elendae]

Nearly everyone already does common core on the fly anyway.

Like, your meal comes to $11.79. You want to give the waitress $15.00.

$11.79 -> $11.80 -> $12.00 -> $15.00

.01 + .20 + 3.00 = $3.21

I was taught the old way, but do it this way in my head in real life situations.