Number.prototype.toFixed is a function designed to format a number before printing it out. It's from the family of toString, toExponential and toPrecision.

To round a number, you would do this:

someNumber = 42.008;
someNumber = Math.round( someNumber * 1e2 ) / 1e2;
someNumber === 42.01;

// if you need 3 digits, replace 1e2 with 1e3 etc.
// or just copypaste this function to your code:

function toFixedNumber(num, digits, base){
  const pow = Math.pow(base ?? 10, digits);
  return Math.round(num*pow) / pow;
}

Why isn't this function included in the JavaScript's standard library? Because floating point numbers are hard! Many decimal numbers cannot be directly represented by base-two floats – that's why 0.09 + 0.01 !== 0.1 but 0.09999999999999999. If developers were given a tool which is supposed to round floats to decimal places, they'd (wrongly) assume that it really returns a decimal number, when it in fact returns the closest representable double-precision base-two float.