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	$50.39	10.791%	$55.8276	$55.83	$55.85	$55.80
Purchase #2	$49.86	6.365%	$53.0336	$53.03	$53.05	$53.00
Purchase #3	$236.80	7.335%	$254.1693	$254.17	$254.15	$254.20
Purchase #4	$223.64	9.443%	$244.7583	$244.76	$244.75	$244.80
Purchase #5	$226.95	12.739%	$255.8612	$255.86	$255.85	$255.90
Purchase #6	$20.65	7.747%	$22.2498	$22.25	$22.25	$22.20
Purchase #7	$205.43	11.381%	$228.81	$228.81	$228.80	$228.80
7 purchase totals =	$1,013.72		$1,114.7098	$1,114.71	$1,114.70	$1,114.70