CREATING ROUND BAR TIP OF THE COLUMN CHART IN POWERPOINT

Make sure the type of chart is 3-D Clustered Column.

Right click the chart -> Format Chart Area -> Chart Options -> Effects -> 3-D Rotation : X Rotation = 0⁰; Y Rotation = 0⁰; Perspective near to 0⁰.

Choose the blue bar and then right click -> Format Data Series -> Effects -> 3-D Format -> Top Bevel : Width =10 pt; Height = 10 pt. Select Material : Flat

Apply the same way to 2 others : orange and grey bar. 

Finish.

Source :
https://answers.microsoft.com/en-us/msoffice/forum/all/how-do-i-make-the-columns-in-my-column-chart-have/94d39e86-2298-4ee8-ba8e-5eaca3e97c66