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	$183.57	3.693%	$190.3492	$190.35	$190.35	$190.30
Purchase #2	$90.44	11.218%	$100.5856	$100.59	$100.60	$100.60
Purchase #3	$80.51	6.756%	$85.9493	$85.95	$85.95	$85.90
Purchase #4	$241.60	11.627%	$269.6908	$269.69	$269.70	$269.70
Purchase #5	$132.87	8.335%	$143.9447	$143.94	$143.95	$143.90
Purchase #6	$173.72	12.629%	$195.6591	$195.66	$195.65	$195.70
Purchase #7	$175.26	8.560%	$190.2623	$190.26	$190.25	$190.30
7 purchase totals =	$1,077.97		$1,176.4410	$1,176.44	$1,176.45	$1,176.40