answer:99 cents. Nothing less will do. If something costs 99 cents and you don’t have it, you will have to pay with a dollar and get an extra penny. If you carry at least 99 cents in change, then for any purchase you will always end up with a dollar less in change than if you did not have enough change to cover the cents in the price. If you start the day with at least 99 cents in change and make multiple purchases, you will always end the day with at most the amount of change you started with. If you are mainly concerned about accumulating pennies, you can always end up with fewer pennies if you carry 4 of them.