I happen to find this out and I'm sure someone will abuse it but I think the devs should know...
If you start the day, not open the store, do all the online orders and quit to main menu, the game will remember how much money you had at the point of quitting - not at the beginning of the day.
It will than act like it is the beginning of the day and give new online orders.
I didn't test it more than 3 times but from what I can tell it will always save the money you had when quitting and always give new orders
this is obviously a money hack since you can just keep doing online orders and don't even need to open the store and progress the day...