Just use Round function
IF NOT OBJECT_ID('ANDRETEST') IS NULL
DROP TABLE ANDRETEST
GO
CREATE TABLE ANDRETEST
(
F1 FLOAT,
F2 CHAR(10)
)
GO
INSERT INTO ANDRETEST ( F1, F2 ) VALUES ( 160.2,'TEST')
INSERT INTO ANDRETEST ( F1, F2 ) VALUES ( 100,'TEST')
INSERT INTO ANDRETEST ( F1, F2 ) VALUES ( 79.5,'TEST')
SELECT ROUND(SUM(F1 - ROUND( F1, 0, 1)), 1) AS TEST FROM ANDRETEST
IF NOT OBJECT_ID('ANDRETEST') IS NULL
DROP TABLE ANDRETEST
GO