Why you want to cover with sand. What is your surrounding look like?

Change the cover to cement slab and done.

Put a geotextile before top up with sand.
Options that you have,
1) Concrete cover (Ready made of cast insitu)
2) Cover with stone
3) Cover with artificial grass
4) Relocate the manhole
Why need to raise 5 inches for artificial grass?
By the way, you can raise the manhole too, then just cut a separate piece artificial grass put on top of the manhole. Like a ceiling access panel concept.