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	$222.66	5.603%	$235.1356	$235.14	$235.15	$235.10
Purchase #2	$120.96	4.325%	$126.1915	$126.19	$126.20	$126.20
Purchase #3	$225.46	13.853%	$256.693	$256.69	$256.70	$256.70
Purchase #4	$139.34	12.436%	$156.6683	$156.67	$156.65	$156.70
Purchase #5	$55.66	7.288%	$59.7165	$59.72	$59.70	$59.70
Purchase #6	$65.57	13.268%	$74.2698	$74.27	$74.25	$74.30
Purchase #7	$99.81	11.229%	$111.0177	$111.02	$111.00	$111.00
7 purchase totals =	$929.46		$1,019.6924	$1,019.70	$1,019.65	$1,019.70