*laughs* You don't need a regex. You need simple CS 101 logic.

my @values = ('5.5', '9', '19.95');
foreach my $value (@values) {
    my $dollars = int $value;
    my $cents = $value - $dollars;
    my $converted_value = sprintf "\$$dollars.%02d", int ($cents * 100
+ + .5);
    print "$converted_value\n";
}

----

$5.50
$9.00
$19.95
[download]

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