SQL: incorrect sum of several FLOAT values

create table xx (key_field INT PRIMARY KEY,field2 FLOAT);
insert into xx (key_field,field2) values (1, 100000);
insert into xx (key_field,field2) values (2, 50000);
insert into xx (key_field,field2) values (3, 30000);
insert into xx (key_field,field2) values (4, 55555.1);
insert into xx (key_field,field2) values (5, 30000);
insert into xx (key_field,field2) values (6, 40000);
insert into xx (key_field,field2) values (7, 20000);
insert into xx (key_field,field2) values (8, 80000);
insert into xx (key_field,field2) values (9, 30000);
insert into xx (key_field,field2) values (10,90000);
insert into xx (key_field,field2) values (11,90000);
SELECT SUM(field2) FROM xx;                                
--> returns 615555.1015625, expected 615555.1