$ perl -e 'printf "13.24 rounds to %.*f0\n", 1, 13.24';
13.24 rounds to 13.20

$ perl -e 'printf "13.25 rounds to %.*f0\n", 1, 13.25';
13.25 rounds to 13.20

$ perl -e 'printf "13.26 rounds to %.*f0\n", 1, 13.26';
13.26 rounds to 13.30

##</code><code>##

> say sprintf("13.24 rounds to %.*f0", 1, 13.24);
13.24 rounds to 13.20

> say sprintf("13.25 rounds to %.*f0", 1, 13.25);
13.25 rounds to 13.30

> say sprintf("13.26 rounds to %.*f0", 1, 13.26);
13.26 rounds to 13.30