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	$41.57	7.257%	$44.5867	$44.59	$44.60	$44.60
Purchase #2	$79.84	5.830%	$84.4947	$84.49	$84.50	$84.50
Purchase #3	$90.97	4.574%	$95.131	$95.13	$95.15	$95.10
Purchase #4	$197.56	10.160%	$217.6321	$217.63	$217.65	$217.60
Purchase #5	$87.52	3.403%	$90.4983	$90.50	$90.50	$90.50
Purchase #6	$246.79	3.509%	$255.4499	$255.45	$255.45	$255.40
Purchase #7	$131.47	6.344%	$139.8105	$139.81	$139.80	$139.80
7 purchase totals =	$875.72		$927.6032	$927.60	$927.65	$927.50