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	$133.40	7.625%	$143.5718	$143.57	$143.55	$143.60
Purchase #2	$202.92	7.151%	$217.4308	$217.43	$217.45	$217.40
Purchase #3	$128.45	11.487%	$143.2051	$143.21	$143.20	$143.20
Purchase #4	$100.32	3.105%	$103.4349	$103.43	$103.45	$103.40
Purchase #5	$88.65	10.585%	$98.0336	$98.03	$98.05	$98.00
Purchase #6	$99.33	12.102%	$111.3509	$111.35	$111.35	$111.40
Purchase #7	$206.89	7.613%	$222.6405	$222.64	$222.65	$222.60
7 purchase totals =	$959.96		$1,039.6676	$1,039.66	$1,039.70	$1,039.60