When I do [multi-day] cons I ALWAYS take my cash home(or back to the hotel room if I'm at an out-of-town show; also when heading back the next day I would never leave yesterday's profit in the room).
Now my stuff(books/prints/stickers)- I'll cover that with a cloth that I sometimes use for table cloth if the con I'm at has their table decked out with a liner on top and a skirt. If I have to use my cloth as decorate for my table, then I put my books, stickers, & prints away but leave my shelves and business cards on the table; I'll usually put my stuff in my totes that I transport everything in and slide them under the table.
Make a mental note how security is; also make friends with some of your surrounding table mates so that you all can watch out for each other.