Percentage from Total SUM after GROUP BY SQL Server

You don't need a cross join. Just use window functions:

SELECT P.PersonID, SUM(PA.Total),
       SUM(PA.Total) * 100.0 / SUM(SUM(PA.Total)) OVER () AS Percentage
FROM Person P JOIN
     Package PA
     ON P.PersonID = PA.PackageFK
GROUP BY P.PersonID;

Note that you do not need the JOIN for this query:

SELECT PA.PersonID, SUM(PA.Total),
       SUM(PA.Total) * 100.0 / SUM(SUM(PA.Total)) OVER () AS Percentage
FROM Package PA
GROUP BY PA.PersonID;

SQL Server does integer division. I do such calculations using decimal numbers so they make more sense.

Here is a SQL Fiddle, with two changes:

1. The database is changed to SQL Server.
2. The total is stored as a number rather than a string.

You can use Common table Expression...

;with cte as(
  select  P.PersonID,SUM(cast(PA.Total as int))Total  from  Package PA join   Person P on P.PersonID = PA.PackageFK GROUP BY P.PersonID 
  )
  select PersonId,Total,cast (Total * 100 / t.GrandTotal as varchar) + '%'  [Percentage] from cte cross join(select SUM(cast(Total as int)) as GrandTotal from Package)t

Try this below code

;With cte(PersonID ,Total)
AS
(
 SELECT  1 ,75 UNION ALL
 SELECT  2 ,75 UNION ALL
 SELECT  3 ,15 UNION ALL
 SELECT  4 ,15 UNION ALL
 SELECT  5 ,60 UNION ALL
 SELECT  6 ,60
 )

SELECT PersonID, 
       Total, 
       CAST(CAST((MAX(total)OVER(partition BY personid ORDER BY total)*100.0/ 
       MaxSum) AS INT)AS VARCHAR(5))+ '%' AS Percentage 
FROM   (SELECT personid, 
               total, 
               stotal, 
               Max(stotal) 
                 OVER( 
                   ORDER BY stotal DESC) AS MaxSum 
        FROM   (SELECT personid, 
                       total, 
                       Sum(total) 
                         OVER( 
                           ORDER BY personid) AS STotal 
                FROM   Cte)dt 
        GROUP  BY dt.personid, 
                  dt.total, 
                  dt.stotal)dt2 
ORDER  BY dt2.personid ASC 

Result

PersonID    Total   Percentage
------------------------------
1            75         25%
2            75         25%
3            15         5%
4            15         5%
5            60         20%
6            60         20%