Double and Single precision, if you want to keep the spec but not to bee to exact. They may also mess up some calculations, be careful.
IF you want to keep all decimals, use a larger integer, like Currency. Or if you want to have a specific decimal point and keep as many decimals (up to 28) you could go for having it stored in a variant as a Decimal datatype. Use CDEC function to convert the variant to Decimal.