MySQL conversion from float (10,2) to fixed(10,2)
BAD NEWS : I do not think the value will be preserved !!!
I wrote this post (July 25, 2011) showing how sensitive floating point numbers are to conversions.
GOOD NEWS : Here is how you can safely compare the data conversion:
If your table has these characteristics

table is called moneytable
field you wish to convert is called moneyfield
primary key is called moneyid

Then run these commands:
DROP TABLE IF EXISTS moneytabletest;
CREATE TABLE moneytabletest LIKE moneytable;
ALTER TABLE moneytabletest MODIFY moneyfield fixed(10,2);
INSERT INTO moneytabletest SELECT * FROM moneytable;
SELECT A.moneyid,A.moneyfield olddata,B.moneyfield newdata
FROM moneytable A LEFT JOIN moneytabletest B USING (moneyid)
WHERE A.moneyfield &lt;&gt; B.moneyfield;

Here is the bottom line: If any rows come back from the LEFT JOIN query, the conversion will be bad. You will have to modify the definition of moneyfield, reload  the moneytabletest table, and run the LEFT JOIN query again and again until no rows come back from the LEFT JOIN query. Once zero(0) rows come back, you will know what conversion will be safe.
Give it a Try !!!