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	$89.75	6.516%	$95.5981	$95.60	$95.60	$95.60
Purchase #2	$94.81	5.544%	$100.0663	$100.07	$100.05	$100.10
Purchase #3	$199.76	11.174%	$222.0812	$222.08	$222.10	$222.10
Purchase #4	$97.77	4.471%	$102.1413	$102.14	$102.15	$102.10
Purchase #5	$215.87	3.487%	$223.3974	$223.40	$223.40	$223.40
Purchase #6	$190.85	10.605%	$211.0896	$211.09	$211.10	$211.10
Purchase #7	$152.77	10.235%	$168.406	$168.41	$168.40	$168.40
7 purchase totals =	$1,041.58		$1,122.7799	$1,122.79	$1,122.80	$1,122.80