i cant group a column in sql server

Question

my table record is below in screen shot 

my query is belw

 

declare @FromDate datetime

set @FromDate='03-01-17'

declare @Todate datetime

set @Todate='03-19-17'

select

sum(round(OThrs,0)) as OThrs, convert(int,round((( ME.AuditSalary+HRA)/8),0)* convert(int,round(isnull(OThrs,0),0)*2)) as OTSalary

from master_salary as MS

inner join Master_Employee as ME on ME.id=MS.Refid

Where convert(varchar(10),MS.Attdate,110) between @FromDate and @Todate and ME.Category in(2)

group by ME.AuditSalary ,HRA,OThrs