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	$131.68	9.109%	$143.6747	$143.67	$143.65	$143.70
Purchase #2	$124.96	6.245%	$132.7638	$132.76	$132.75	$132.80
Purchase #3	$217.82	5.600%	$230.0179	$230.02	$230.00	$230.00
Purchase #4	$114.65	4.244%	$119.5157	$119.52	$119.50	$119.50
Purchase #5	$69.97	3.602%	$72.4903	$72.49	$72.50	$72.50
Purchase #6	$100.57	10.544%	$111.1741	$111.17	$111.15	$111.20
Purchase #7	$236.47	7.243%	$253.5975	$253.60	$253.60	$253.60
7 purchase totals =	$996.12		$1,063.2340	$1,063.23	$1,063.15	$1,063.30