Javascript decimal calculation for the pre assume value as like Numi app

Question

The attached diagram shows the correct results in Numi app in IOS. When i calculate the same calculation, it calculates differently. I want the same way as how Numi did on the image.

amount = 4;
commission = 0.5; 
round = 6;
result = amount / (1 + commission / 100);
fee = result * (commission / 100)
total = result + fee

Here the total value must be equal to the given amount for any input. Js results 4.000001 if i set decimal precision to 6

testFunction(4);

function testFunction(amount) {
  const commission = 0.5;
  const round = 6;

  const finalAmount = amount / (1 + commission / 100);
  const result = roundOff(finalAmount, round);
  const fee = roundOff(result * (commission/100), round);
  const total = roundOff(result + fee, round);
  if(amount > total || amount < total)
  console.log("Qty: " + result + " fee: " + fee + " Total = "+ total);
  return total;
}

function roundOff (x, n) {
 return Number(parseFloat(Math.round(x * Math.pow(10, n)) / Math.pow(10, n)).toFixed(n));
}