sql function - round float to sig fig

RoundSigFig.sql

GO
CREATE FUNCTION RoundSigFig(@Number float, @Figures int)
RETURNS float
AS
BEGIN

    DECLARE @Answer float;

    SET @Answer = (
    SELECT
        CASE WHEN intPower IS NULL THEN 0
        ELSE FLOOR(fltNumber * POWER(CAST(10 AS float), intPower) + 0.5) 
                        * POWER(CAST(10 AS float), -intPower)
        END AS ans
    FROM (
        SELECT
            @Number AS fltNumber,
            CASE WHEN @Number > 0
                THEN -((CEILING(LOG10(@Number)) - @Figures))
            WHEN @Number < 0
                THEN -((FLOOR(LOG10(@Number)) - @Figures))
            ELSE NULL END AS intPower           
        ) t
    );

    RETURN @Answer;
END;
GO

declare @SigFigRight float;
select dbo.RoundSigFig(1806.6600958604099,15);

SFRound.sql

create function sfround(@number float, @sf int) returns float as
begin
    declare @r float
    select @r = case when @number = 0 then 0 else round(@number ,@sf -1-floor(log10(abs(@number )))) end
    return (@r)
end

I've since discovered that this function throws an error for negative values. Now using the second function.

Source:
http://stackoverflow.com/questions/1920933/round-to-n-significant-figures-in-sql