decimal figures

As my prices I need 5 decimals in all the figures fields. As far as prices I changed the settings but I can't do it as the fixed fields "SUBTOTALS" or "TAX", "ADJUSTMENT""(ex: QUOTES - My prices have more than 2 decimals but I can't save it because the fixed fields are setted for two decimals only and when I save the software generates a "error" message. How can I modify the setting?
ROBERTO TIMITILLI