Here my brutal attempt translating in perl what i'd say in plain language. Note the *10 at the begin and the /10 at the end: they make your life easier confining the problem to one digit only.

use strict;
use warnings;

print map {
            my ($int,$dec)=split /\./,$_*10;
            $dec = defined $dec && $dec >= 5 ? 1 : 0;
            sprintf("%.2f\n", ($int+$dec)/10);
      } (<DATA>);
__DATA__
1.24
13.25
2.90
2.99
2.92
14

# OUT
1.20
13.30
2.90
3.00
2.90
14.00
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HtH

L*