The store doesn't even need to be big, just enough a sim can enter then come out with whatever they bought.
If it's drink or snacks then they should go stand or sit somewhere like those park tables perhaps, and consume the drink or snacks.
if it's a ticket it is maybe put into the sims pocket after exiting the store, sending the ticket to the sims inventory for storage.
RNG could determine the individual ticket numbers as well as the weekly winning numbers.
Old tickets should automatically vanish after sending a Sim back to the store after the lotto numbers are released, to "check lottery ticket" to see if they have won.
Each ticket should be able to be checked as long as it is before the next draw date. Unchecked old tickets leave a message in the inbox of it's result if missed checking the ticket and the ticket should vanish.