The problem is deeper than simply entering the percentages manually. For a given charity, sometimes the total donated amount is the sum of donations including cash donations, mileage, physical goods, and appreciated financial instruments. Unfortunately, only some of those are 100% donations, so it is impossible to pick a single classification for an organization, unless you make multiple entries for those organizations to which you donated both 50/60 items and 100% items.
TurboTax blew it badly this year and the charitable contributions sections needs a total rewrite (and it's too late for that). Oddly this is solved by competing tax softwares.
