wrong decimal sum when using FLOAT type

To reproduce the error, build this table as example:

{{CREATE TABLE `test` (
`FACTURA` CHAR(20) NULL DEFAULT NULL,
`FECHA` DATE NULL DEFAULT NULL,
`IMPORTE` FLOAT NULL DEFAULT NULL
);}}

It only need a 1 record, but you must use any. Use this for example:

{{INSERT INTO `test` (`FACTURA`, `FECHA`, `IMPORTE`) VALUES
('BE6141', '2016-06-14', 877.8);
}}

Finally, run this query:

{{select factura, CONCAT_WS(',',FECHA) as FECHA, SUM(importe) AS IMPORTE
from test
group by factura;
}}

The result is:
------------------------------------
| factura | FECHA | IMPORTE |
------------------------------------
| BE6141 | 2016-06-14 | 877.7999877929688 |
------------------------------------
1 row in set (0.00 sec)

As you can see = 877.7999877929688 <> 877.8