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	$248.65	4.444%	$259.7	$259.70	$259.70	$259.70
Purchase #2	$143.50	8.468%	$155.6516	$155.65	$155.65	$155.70
Purchase #3	$142.32	12.654%	$160.3292	$160.33	$160.35	$160.30
Purchase #4	$229.54	7.734%	$247.2926	$247.29	$247.30	$247.30
Purchase #5	$128.29	11.688%	$143.2845	$143.28	$143.30	$143.30
Purchase #6	$183.98	6.471%	$195.8853	$195.89	$195.90	$195.90
Purchase #7	$100.57	10.514%	$111.1439	$111.14	$111.15	$111.10
7 purchase totals =	$1,176.85		$1,273.2871	$1,273.28	$1,273.35	$1,273.30