After drawing the box make sure you curve the edges

By doing the following:

1-

Go to full view to look at it well

2-

Convert to editable polly

3-

Select the bottom and 2 edges

4-

Choose edge tool(the 2

nd

red choice)

5-

Go to chamfer

6-

And choose segments and sides

Now create a dint in the top. 

Through polygon Then click insert vertex Then move it down

Now create the top by creating a cylinder and while doing so put the segments on the side

Then convert the cylinder to editable poly by right clicking it

Then select the points through the first selection

Results