1、去尾法用ROUNDDOWN函数
2、收尾法用ROUNDUP函数
3、四舍五入法用ROUND函数
4、四舍六入五成双法用IF、ROUNDDOWN、ROUNDUP和ROUND函数等
示例:

=ROUNDDOWN(A2,1)

=ROUNDUP(A2,1)

=ROUND(A2,1)

=IF(OR(--RIGHT(ROUNDDOWN(A2,2))<5,--RIGHT(ROUNDDOWN(A2,2))>5),ROUND(A2,1),IF(ISODD(--RIGHT(ROUNDDOWN(A2,1))),ROUNDUP(A2,1),ROUNDDOWN(A2,1)))