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	$224.46	4.119%	$233.7055	$233.71	$233.70	$233.70
Purchase #2	$204.92	8.572%	$222.4857	$222.49	$222.50	$222.50
Purchase #3	$223.65	4.741%	$234.2532	$234.25	$234.25	$234.30
Purchase #4	$129.25	6.356%	$137.4651	$137.47	$137.45	$137.50
Purchase #5	$59.67	4.551%	$62.3856	$62.39	$62.40	$62.40
Purchase #6	$113.88	10.733%	$126.1027	$126.10	$126.10	$126.10
Purchase #7	$5.36	13.727%	$6.0958	$6.10	$6.10	$6.10
7 purchase totals =	$961.19		$1,022.4936	$1,022.51	$1,022.50	$1,022.60