code: public static String round(String value, int scale) {
          BigDecimal bd;
          try {
              bd = new BigDecimal(value);
              bd = bd.setScale(scale, RoundingMode.HALF_UP);
              return bd.toString();
          } catch (Exception e) {
              return null;
          }
      }
docs: Returns the closest {@code decimal} to the argument, with given scale,
  using HALF_UP mode
  
  Any numeric string recognized by {@code BigDecimal} is supported.
  
  @param value A valid number string
  
  @return the rounded number.
  
  @see BigDecimal