How to Create a Case Statement to Classify / Segment Data

Can someone show me how to create a case statement that will classify the sample data below to appear as follows:

At the moment the table in SQL looks like the following:

Sample data is as follows:

CREATE TABLE #tmpTable (
Channel nvarchar(50),
Months nvarchar(50),
Total Sales int)

INSERT #tmpTable VALUES
(N'Online',N'Jan',1427),
(N'Online',N'Feb',1486),
(N'Online',N'Mar',1325),
(N'Online',N'Apr',1065),
(N'Online',N'May',803),
(N'Online',N'Jun',661),
(N'Online',N'Jul',665),
(N'Online',N'Aug',912),
(N'Online',N'Sep',1444),
(N'Online',N'Oct',1689),
(N'Online',N'Nov',1763),
(N'Online',N'Dec',1440),
(N'Social Media',N'Jan',1025),
(N'Social Media',N'Feb',925),
(N'Social Media',N'Mar',769),
(N'Social Media',N'Apr',555),
(N'Social Media',N'May',412),
(N'Social Media',N'Jun',325),
(N'Social Media',N'Jul',341),
(N'Social Media',N'Aug',495),
(N'Social Media',N'Sep',949),
(N'Social Media',N'Oct',1126),
(N'Social Media',N'Nov',1273),
(N'Social Media',N'Dec',1067),
(N'Outlet',N'Jan',125),
(N'Outlet',N'Feb',96),
(N'Outlet',N'Mar',73),
(N'Outlet',N'Apr',88),
(N'Outlet',N'May',65),
(N'Outlet',N'Jun',53),
(N'Outlet',N'Jul',45),
(N'Outlet',N'Aug',66),
(N'Outlet',N'Sep',145),
(N'Outlet',N'Oct',199),
(N'Outlet',N'Nov',202),
(N'Outlet',N'Dec',181),
(N'Stores',N'Jan',639),
(N'Stores',N'Feb',641),
(N'Stores',N'Mar',418),
(N'Stores',N'Apr',398),
(N'Stores',N'May',329),
(N'Stores',N'Jun',306),
(N'Stores',N'Jul',258),
(N'Stores',N'Aug',398),
(N'Stores',N'Sep',701),
(N'Stores',N'Oct',879),
(N'Stores',N'Nov',961),
(N'Stores',N'Dec',818)

SELECT * FROM #tmpTable

Thank you