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	$190.44	11.286%	$211.9331	$211.93	$211.95	$211.90
Purchase #2	$100.37	8.485%	$108.8864	$108.89	$108.90	$108.90
Purchase #3	$138.70	3.764%	$143.9207	$143.92	$143.90	$143.90
Purchase #4	$176.44	12.720%	$198.8832	$198.88	$198.90	$198.90
Purchase #5	$198.32	6.636%	$211.4805	$211.48	$211.50	$211.50
Purchase #6	$144.72	4.724%	$151.5566	$151.56	$151.55	$151.60
Purchase #7	$13.56	6.562%	$14.4498	$14.45	$14.45	$14.40
7 purchase totals =	$962.55		$1,041.1103	$1,041.11	$1,041.15	$1,041.10