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	$63.31	11.574%	$70.6375	$70.64	$70.65	$70.60
Purchase #2	$194.98	13.372%	$221.0527	$221.05	$221.05	$221.10
Purchase #3	$105.25	5.758%	$111.3103	$111.31	$111.30	$111.30
Purchase #4	$160.55	5.231%	$168.9484	$168.95	$168.95	$168.90
Purchase #5	$60.94	8.191%	$65.9316	$65.93	$65.95	$65.90
Purchase #6	$177.86	11.489%	$198.2943	$198.29	$198.30	$198.30
Purchase #7	$48.33	4.507%	$50.5082	$50.51	$50.50	$50.50
7 purchase totals =	$811.22		$886.6830	$886.68	$886.70	$886.60