Yes this is possible. 

You can hide any menu by following way.

1. Create a group like "Usability/Thrash". Don't add any user into it. ( Not admin too )

2. Add that menu which you don't want to show to anybody into that group. ( "Usability/Thrash" )

By doing so, that menu will not be visible under "Sales" to anybody. 

Note : 

1. Here, it is not necessary to create new group. You can use any of current groups but take care that no body shall be inside that group. ( Because you don't want to show that menu to anyone. )

2. By adding just group to that menu, it doesn't means that Sales order will completely hidden. Just that menu will be removed from menu list. However where there is M2O of sale.order, Orders will be still visible on that field. In order to remove order from there too, you need to manage access rights and record rules.

I Hope this helps ,