What version are you using?
Tested in a 2.3 environment and it worked fine when I was in Categories & Items and selected the Show/Hide icon next to the course total; hid the total but not any individual grade items.
I remember in 1.9 it was a multi-step process as it was a workaround.
- In gradebook, select My Preferences tab. If needed, change Show show/hide icons to Yes.
- Go to Categories & Items and select the Hide icon to the right of the course total at the very bootom. The open eyeball icon will turn to a closed eyeball icon.
- Go to the Grader Report and turn editing on.
- Select the closed eyeball icon next to the name of the course at the top of the screen. The closed eyeball icon will turn to an open icon. DO NOT select the course total icon on this screen.