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	$201.49	11.733%	$225.1308	$225.13	$225.15	$225.10
Purchase #2	$55.43	13.444%	$62.882	$62.88	$62.90	$62.90
Purchase #3	$48.56	12.766%	$54.7592	$54.76	$54.75	$54.80
Purchase #4	$60.31	7.684%	$64.9442	$64.94	$64.95	$64.90
Purchase #5	$58.32	6.780%	$62.2741	$62.27	$62.25	$62.30
Purchase #6	$103.94	6.771%	$110.9778	$110.98	$111.00	$111.00
Purchase #7	$9.65	11.119%	$10.723	$10.72	$10.70	$10.70
7 purchase totals =	$537.70		$591.6911	$591.68	$591.70	$591.70