Answer to a StackOverflow question locked by idiots...

answer.md

Answer for: http://stackoverflow.com/questions/41154976/php-rounding-number-cant-round

Because round() returns a float, and 68.45 can't be accurately represented at high precisions. In this case, 16 digits or higher.

Eg:

function test($number, $precision) {
    ini_set('precision', $precision);
    var_dump(
        $number,
        round($number, 2),
        number_format($number, 2),
        sprintf("%4.2f", $number)
    );
    echo "\n";
}

$a = 68.45999999999999;
$b = 68.46;
echo "== Precision 15 ==\n";
test($a, 15);
test($b, 15);
echo "== Precision 16 ==\n";
test($a, 16);
test($b, 16);

Output:

== Precision 15 ==
float(68.46)
float(68.46)
string(5) "68.46"
string(5) "68.46"

float(68.46)
float(68.46)
string(5) "68.46"
string(5) "68.46"

== Precision 16 ==
float(68.45999999999999)
float(68.45999999999999)
string(5) "68.46"
string(5) "68.46"

float(68.45999999999999)
float(68.45999999999999)
string(5) "68.46"
string(5) "68.46"

Use number_format() or [s]printf() as also illustrated in the example. However, if you are trying to accurately round a float to two digits you really should read up on how floats work...