Solusi Pembulatan dari penjumlahan Beberapa nilai desimal

Assalam, coba share nilai desimal yang ditambahkan tersebut mas...
agar bisa kita cobakan disini, biar lebih cepat kelarnya,.. :)

dikoding nya spt ini contoh hitungannya:
 
<?php
$x1=2174436;
$x2=$x1*0.4;
echo "x1=$x1 <br>x2=40% dr x1=$x2<br>";
$z1=9*(0.04*$x2);
echo "z1=9x(4% dr x2)=".$z1;
$z2=2*(0.005*$x2);
echo "<br>z2=2x(0.5% dr x2)=".$z2;
$z3=2*(0.005*$x2);
echo "<br>z3=2x(0.5% dr x2)=".$z3;
$z4=2*(0.015*$x2);
echo "<br>z4=2x(1.5% dr x2)=".$z4;
$z5=22*(0.01*$x2);
echo "<br>z5=22x(1% dr x2)=".$z5;
$total=$z1+$z2+$z3+$z4+$z5;
echo "<br>Total z1 s/d z5=".$total;
?>
 
<br />penjumlahan di atas sdh benar.
<br />
<br />sekarang dgn memberi number_format.
<br />
<?php
$x1=2174436;
$x2=$x1*0.4;
echo "x1=".number_format($x1, 2, ',', '.')."<br>x2=40% dr x1=".number_format($x2, 2, ',', '.')."<br>";
$z1=9*(0.04*$x2);
echo "z1=9x(4% dr x2)=".number_format($z1, 2, ',', '.');
$z2=2*(0.005*$x2);
echo "<br>z2=2x(0.5% dr x2)=".number_format($z2, 2, ',', '.');
$z3=2*(0.005*$x2);
echo "<br>z3=2x(0.5% dr x2)=".number_format($z3, 2, ',', '.');
$z4=2*(0.015*$x2);
echo "<br>z4=2x(1.5% dr x2)=".number_format($z4, 2, ',', '.');
$z5=22*(0.01*$x2);
echo "<br>z5=22x(1% dr x2)=".number_format($z5, 2, ',', '.');
$total=$z1+$z2+$z3+$z4+$z5;
echo "<br>Total z1 s/d z5=".number_format($total, 2, ',', '.');
?>
<br />kalo dijumlah pake kalkulator, jumlah total: 547.957,86 sedang pake aplikasi 547.957,87

Bukankah yang hitung dari aplikasi sudah benar,
hasilnya memang 547.957,87, bukan 547.957,86,..

Atau coba perbaiki jadi begini saja :
<?php
$x1=2174436;
$x2=$x1*0.4;
echo "x1=".number_format($x1, 2, ',', '.')."<br>x2=40% dr x1=".number_format($x2, 2, ',', '.')."<br>";
$z1=9*(0.04*$x2);
echo "z1=9x(4% dr x2)=".number_format($z1, 2, ',', '.');
$z2=2*(0.005*$x2);
echo "<br>z2=2x(0.5% dr x2)=".number_format($z2, 2, ',', '.');
$z3=2*(0.005*$x2);
echo "<br>z3=2x(0.5% dr x2)=".number_format($z3, 2, ',', '.');
$z4=2*(0.015*$x2);
echo "<br>z4=2x(1.5% dr x2)=".number_format($z4, 2, ',', '.');
$z5=22*(0.01*$x2);
echo "<br>z5=22x(1% dr x2)=".number_format($z5, 2, ',', '.');
$total=$z1+$z2+$z3+$z4+$z5;
function numberFormat($number){
	$ex = explode('.', $number);
	$data = substr($ex[1], 0,2);
	if (substr($ex[1], 2,1)<5){
		$hitung = substr($ex[1], 0,2)-1;
	}else{
		$hitung = substr($ex[1], 0,2)+1;
	}
		return number_format($ex[0], 0, ',', '.').','.$hitung;
}
echo "<br>Total z1 s/d z5=".numberFormat($total);
?>
 
// Hasilnya : 547.957,86