$ perl -e 'print "raw\t\trounded\n"; printf "%f\t%.0f\n", $_+0.5,  $_+0.5 for 0..10; '
raw             rounded
0.500000        0
1.500000        2
2.500000        2
3.500000        4
4.500000        4
5.500000        6
6.500000        6
7.500000        8
8.500000        8
9.500000        10
10.500000       10