The numbers in your latest post, 30, 23, and 13, happen to be what I gather your mean by a "nice" case; that is, when calculated as percentages of their total and rounded, the percentages add up (nicely) to 100.

Here's a case where the numbers are not "nice" and where a disclaimer is the only reasonable solution (fudging is NOT, IMO, reasonable):

#!/usr/bin/perl
use strict;
use warnings;
#785290

my $Google=30; my $Yahoo=23; my $Bing=12;
my $sum=$Google + $Yahoo + $Bing;

my $google_percent = $Google/$sum;
print "G: $google_percent";
my $yahoo_percent = $Yahoo/$sum;
print "\tY: $yahoo_percent";
my $bing_percent = $Bing/$sum;
print "\tB: $bing_percent \n";

my $total = ($google_percent + $yahoo_percent + $bing_percent);

my $roundedG = sprintf("%.2f", $google_percent);
my $roundedY = sprintf("%.2f", $yahoo_percent);
my $roundedB = sprintf("%.2f", $bing_percent);
my $rounded = sprintf("%.2f", $total);
print "Google: $roundedG; Yahoo: $roundedY; Bing: $roundedB; Total: $r
+ounded \n";

printf ('%.0f', (($Google/$sum)*100));
print "%\n";
printf ('%.0f', (($Yahoo/$sum)*100));
print "%\n";
printf ('%.0f', (($Bing/$sum)*100));
print "%\n";
print $rounded*100 . "% (Percentages may not add up to 100 because of 
+rounding errors!)\n";
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