Basic question about adding numbers from DB

Hi, I have some prices stored in a table, and after retrieving records
like,

2.50
1.70
3.25
4.25

I add them together with something like,

<?php for ($x = 0; $x < sizeof($prices); $x++) {
$total=$total+$prices[$x]; }?>

But, when I print $total, if the amounts add up to an even number like
11.70, it prints out like 11.7

How do I get this to express any zeros at the end? Best regards, Amy

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