http://i.imgur.com/ZCRcXhN.png
Tooltips and displayed values get rounded.
Tryndamere's HP5 at level 1 is 8.51 + .9. 8.51 rounds to 9. .9 rounds to 1. Their sum is 9.41, which rounds to 9.
2+2=5 for extraordinarily large values of 2.