before		after
1	function total ( $rows ) {	1	function total ( $rows, $tax = 0.21 ) {
2	$sum = 0;	2	$sum = 0;
3	foreach ( $rows as $row )	3	foreach ( $rows as $row )
4	$sum += $row ['price'];	4	$sum += $row ['price'] * $row ['quantity'];
5	return $sum;	5	return round ( $sum * ( 1 + $tax ), 2 );
6	}	6	}