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	$52.38	4.663%	$54.8225	$54.82	$54.80	$54.80
Purchase #2	$11.52	5.729%	$12.18	$12.18	$12.20	$12.20
Purchase #3	$98.97	13.103%	$111.938	$111.94	$111.95	$111.90
Purchase #4	$30.25	9.740%	$33.1964	$33.20	$33.20	$33.20
Purchase #5	$111.97	5.133%	$117.7174	$117.72	$117.70	$117.70
Purchase #6	$84.66	6.371%	$90.0537	$90.05	$90.05	$90.10
Purchase #7	$77.66	11.537%	$86.6196	$86.62	$86.60	$86.60
7 purchase totals =	$467.41		$506.5276	$506.53	$506.50	$506.50