function calculateTax(overallSum, result) {
  var sum;
  if(typeof overallSum == "undefined" || overallSum == "" || overallSum === null) {
    return;
  } else if(typeof overallSum == "number") {
    sum = overallSum;
  } else if(typeof overallSum == "object") {
    sum = overallSum.innerText || overallSum.textContent;
  } else if(typeof overallSum == "string") {
    if(!document.getElementById(overallSum)) return;
    sum = document.getElementById(overallSum).innerText || document.getElementById(overallSum).textContent;
  }

  sum = parseFloat(sum);
  sum = sum * 0.2;
  sum = Math.round(sum*100)/100;
  sum = sum.toString().replace('.', ',');
  
  if(typeof result == "undefined" || result == "" || result === null) {
    return sum;
  } else if(typeof result == "object") {
    result.innerHTML = sum;
  } else if(typeof result == "string") {
    if(!document.getElementById(result)) return;
    document.getElementById(result).innerHTML = sum;
  }
}