Try using this version of the money_format () function:
money_format('%.0n', $mon);
According to PHP documentation on money_format ( http://us.php.net/manual/en/function.money-format.php ), formatting the string "% .2n" will make the number appear with a decimal point and two decimal places to the right of the decimal point , regardless of what the cents are, and then format the number according to the format of the national currency in national currency.
"%.0n", . , , .00. .00, , $mon , , "% 0.2n".