Merge pull request #1 from woothemes/master

Update
Update class-wc-tax.php

Compound tax rate calculation is wildly off.

Current tax settings : http://cld.wthms.co/Qeb6

Cart before proposed change : http://cld.wthms.co/ILXk

Cart after proposed change : http://cld.wthms.co/fjWO
Merge pull request #4945 from ChromeOrange/master

Compound tax rate calculation is wildly off.