Math.round() will return the nearest integer value as described here
For your input Math.round(1.53*20)/20
it will first calculate 1.53*20
answer is 30.6 Then your expression becomes
Math.round(30.6)/20
After that result of Math.round(30.6)
is 31 (nearest integer)
Then your statement becomes 31/20
which is 1.55
solved Why does Math.round(1.53*20)/20 = 1.55? How does this actually work?