Add a summary row with totals

Try to use union all as below

SELECT [Type], [Total Sales] From Before
union all
SELECT 'Total', Sum([Total Sales]) From Before

if you have problem with ordering, as i-one suggested try this:

select [Type], [Total Sales] 
from (SELECT [Type], [Total Sales], 0 [Key] 
      From Before 
      union all 
      SELECT 'Total', Sum([Total Sales]), 1 From Before) sq 
order by [Key], Type

You could use the ROLLUP operator

SELECT  CASE 
            WHEN (GROUPING([Type]) = 1) THEN 'Total'
            ELSE [Type] END AS [TYPE]
        ,SUM([Total Sales]) as Total_Sales
From    Before
GROUP BY
        [Type] WITH ROLLUP

This is the more powerful grouping / rollup syntax you'll want to use in SQL Server 2008+. Always useful to specify the version you're using so we don't have to guess.

SELECT 
  [Type] = COALESCE([Type], 'Total'), 
  [Total Sales] = SUM([Total Sales])
FROM dbo.Before
GROUP BY GROUPING SETS(([Type]),());

Craig Freedman wrote a great blog post introducing GROUPING SETS.

If you are on SQL Server 2008 or later version, you can use the ROLLUP() GROUP BY function:

SELECT
  Type = ISNULL(Type, 'Total'),
  TotalSales = SUM(TotalSales)
FROM atable
GROUP BY ROLLUP(Type)
;

This assumes that the Type column cannot have NULLs and so the NULL in this query would indicate the rollup row, the one with the grand total. However, if the Type column can have NULLs of its own, the more proper type of accounting for the total row would be like in @Declan_K's answer, i.e. using the GROUPING() function:

SELECT
  Type = CASE GROUPING(Type) WHEN 1 THEN 'Total' ELSE Type END,
  TotalSales = SUM(TotalSales)
FROM atable
GROUP BY ROLLUP(Type)
;