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	$57.77	8.218%	$62.5175	$62.52	$62.50	$62.50
Purchase #2	$48.88	11.729%	$54.6131	$54.61	$54.60	$54.60
Purchase #3	$69.31	4.801%	$72.6376	$72.64	$72.65	$72.60
Purchase #4	$183.66	12.193%	$206.0537	$206.05	$206.05	$206.10
Purchase #5	$99.61	11.385%	$110.9506	$110.95	$110.95	$111.00
Purchase #6	$246.57	10.501%	$272.4623	$272.46	$272.45	$272.50
Purchase #7	$108.47	6.162%	$115.1539	$115.15	$115.15	$115.20
7 purchase totals =	$814.27		$894.3887	$894.38	$894.35	$894.50