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	$52.54	8.195%	$56.8457	$56.85	$56.85	$56.80
Purchase #2	$120.61	4.527%	$126.07	$126.07	$126.05	$126.10
Purchase #3	$10.58	8.670%	$11.4973	$11.50	$11.50	$11.50
Purchase #4	$18.29	3.578%	$18.9444	$18.94	$18.95	$18.90
Purchase #5	$43.53	3.618%	$45.1049	$45.10	$45.10	$45.10
Purchase #6	$107.43	8.116%	$116.149	$116.15	$116.15	$116.10
Purchase #7	$108.62	5.208%	$114.2769	$114.28	$114.30	$114.30
7 purchase totals =	$461.60		$488.8882	$488.89	$488.90	$488.80