Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$159.29	13.325%	$180.5154	$180.52	$180.50	$180.50
Purchase #2	$20.92	7.468%	$22.4823	$22.48	$22.50	$22.50
Purchase #3	$88.89	13.186%	$100.611	$100.61	$100.60	$100.60
Purchase #4	$147.26	4.403%	$153.7439	$153.74	$153.75	$153.70
Purchase #5	$113.49	11.477%	$126.5152	$126.52	$126.50	$126.50
Purchase #6	$183.62	13.489%	$208.3885	$208.39	$208.40	$208.40
Purchase #7	$137.61	5.225%	$144.8001	$144.80	$144.80	$144.80
7 purchase totals =	$851.08		$937.0564	$937.06	$937.05	$937.00