This should be how both the iPhone and Android app work at this point (please let us know if this is broken for you on either of those). We still have not fixed this issue on the website, though it is something we plan to do.
Realy annoying that you can't enter bill's in form of: 2,3€ whicht will set the amount to 23€...
In the app it works perfectly. I don't think its a big deal to change this cause its only on the webside and no app-update is needed.