Convert from scientific notation

Question

Can someone help me with this? I cannot get this working even using some of the tips I found on this site and elsewhere:
Round this and format this with 2 decimals: '-2.58069E-11'.
Now I realize this would end up -2.58, but it is giving me an error instead.
Error converting data type varchar to numeric.
SELECT CAST('2.58069E-11' AS NUMERIC(24,2))
SELECT CAST('2.58069E-11' AS NUMERIC(24,12))
I tried 12 just to make sure that there was enough room for the decimals
If I use ISNUMERIC, it returns 1, so SQL Server considers it a number (at least with that function)
The next example works, but it is not what I want.
SELECT CAST('2.58069E-11' AS REAL) just returns the same thing with the 'E', (as REAL, of course)
In these example I haven't done the rounding yet.
I get all kinds of negative and positive numbers with different decimal lengths, but the scientific notation is particularly tricky.

Answer 1

Before I put this to bed, I have found out both the above solutions are wrong when using a regular decimal:
Try this:
SELECT CAST(CAST('-1131658.27' AS REAL) AS NUMERIC(24,2))
And this:
SELECT CAST(CONVERT(REAL, -1131658.27) as DECIMAL(24,12))
They both yield -1131658.25, and -1131658.250000000000, respectively.
This is probably some floating point error, but how do I take care of it?