Add Total Row To PIVOT Query
The optional WITH ROLLUP clause can be added to your GROUP BY in order to get the grand total row.
GROUP BY employeeName WITH ROLLUP

To get &quot;TOTAL&quot; as the label, you can use the GROUPING function.
Select 
CASE WHEN GROUPING(employeename) = 1 THEN 'TOTAL' ELSE employeeName END

The final query looks like this:
Select 
CASE WHEN GROUPING(employeename) = 1 THEN 'TOTAL' ELSE employeeName END
,SUM(January) As JanAMt
,SUM(February) As FebAMt
,SUM(March) As MarAMt
,SUM(April) As AprAMt
,SUM(May) As MayAMt
,SUM(June) As JunAMt
,SUM(July) As JulAMt
,SUM(August) As AugAMt
,SUM(September) As SepAMt
,SUM(October) As OctAMt
,SUM(November) As NovAMt
,SUM(December) As DecAMt
FROM #empSales
PIVOT ( 
    SUM(saleAmt) For saleMonth IN (January, February, March, April, May, June, July, August, September, October, November, December)
) As pvt
GROUP BY employeeName WITH ROLLUP
Order By GROUPING(employeename), employeeName


Notice that I tweaked the ORDER BY so that the total row comes last in the resultset.