Fix ROUNDUP and ROUNDDOWN for floating-point rounding error

[n-longcape]

This is:

- [x] a bugfix

Checklist:

• Changes are covered by unit tests
• Code style is respected
• Commit message explains why the change is made (see https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• CHANGELOG.md contains a short summary of the change - not needed
• Documentation is updated as necessary -not needed

Why this change is needed?

ROUNDUP and ROUNDDOWN are often different from Excel calculation result because of Floating point precision. PHP Official Document

example

I expected =ROUNDUP(SUM(2.21,2.19), 2) equals 4.4 but 4.41 and =ROUNDDOWN(SUM(2.26,2.94),2) equals 5.2 but 5.19

<?php

require __DIR__ . '/vendor/autoload.php';

use PhpOffice\PhpSpreadsheet\Spreadsheet;

$excel = new Spreadsheet();
$sheet = $excel->getActiveSheet();

// Sample Data
$sheet->setCellValue('A1', '2.21');
$sheet->setCellValue('A2', '2.19');
$sheet->setCellValue('A3', '2.26');
$sheet->setCellValue('A4', '2.94');

$sheet->setCellValue('B1', '=ROUNDUP(SUM(A1:A2), 2)');
$result = $sheet->getCell('B1')->getFormattedValue();
var_dump($result); // "4.41" 
var_dump(number_format(2.21 + 2.19, 20)); // "4.40000000000000035527"

$sheet->setCellValue('B2', '=ROUNDDOWN(SUM(A3:A4),2)');
$result2 = $sheet->getCell('B2')->getFormattedValue();
var_dump($result2); // 5.19
var_dump(number_format(2.26 + 2.94, 20)); // "5.19999999999999928946"
var_dump(number_format(5.2, 20)); // "5.20000000000000017764"