Here's an idea (that may or may not be a minor tweak).
How about a more interactive environment? Like making cash registers, desks, etc into containers. They could hold useful and non-useful items (like say maybe a desk in Chinatown or Hollywood has bubble gum)
Also, give items which currently have a worth of $0 worth something (even quest items - where it makes sense). Bubblegum as an example could be worth $1 when you sell it. Other things like that which add a bit of flavour and allows you to unclutter your inventory.