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	$202.71	4.418%	$211.6657	$211.67	$211.65	$211.70
Purchase #2	$84.92	12.724%	$95.7252	$95.73	$95.75	$95.70
Purchase #3	$105.81	12.864%	$119.4214	$119.42	$119.40	$119.40
Purchase #4	$111.43	6.762%	$118.9649	$118.96	$118.95	$119.00
Purchase #5	$138.73	3.720%	$143.8908	$143.89	$143.90	$143.90
Purchase #6	$190.39	5.197%	$200.2846	$200.28	$200.30	$200.30
Purchase #7	$190.39	4.593%	$199.1346	$199.13	$199.15	$199.10
7 purchase totals =	$1,024.38		$1,089.0872	$1,089.08	$1,089.10	$1,089.10