Always display at least two decimal places

How about using Intl :

Intl.NumberFormat(navigator.language, {
  minimumFractionDigits: 2,
  maximumFractionDigits: 10,
}).format(num)

You could fix to 2 or the count of current places;

 var result = num.toFixed(Math.max(2, (num.toString().split('.')[1] || []).length));