The Excel Floor.Precise function is one of fifteen rounding functions in Excel.
A full list, along with comparison tables, is provided on the Excel Rounding Functions page.The Excel Floor.Precise function rounds a supplied number down to a supplied multiple of significance.
I.e. Positive values are rounded towards zero (becoming less positive) and negative numbers are rounded away from zero (becoming more negative).
The syntax of the Floor.Precise function is:
Where the arguments are listed in the table below:
number    The number that is to be rounded down. 
[significance]    An optional argument that specifies the multiple of significance to round the supplied number down to. If omitted, the [significance] argument takes on the default value 1 (i.e. round down to the nearest integer). 
Note that the arithmetic sign of the [significance] argument is ignored. The supplied number is rounded down for both positive and negative [significance] values.
In column B of the following spreadsheet, the Excel Floor.Precise function is used to round down the positive and negative numbers 26.75 and 26.75, to several different significance values.
Formulas:
 Results:

The above examples show how:
Further details and examples of the Excel Floor.Precise function are provided on the Microsoft Office website.
If you get an error from the Excel Floor.Precise function, this is likely to be the #VALUE! error:
#VALUE!    Occurs if one or both of the supplied arguments are nonnumeric. 