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	$61.89	7.384%	$66.46	$66.46	$66.45	$66.50
Purchase #2	$163.97	5.811%	$173.4983	$173.50	$173.50	$173.50
Purchase #3	$64.41	11.621%	$71.8951	$71.90	$71.90	$71.90
Purchase #4	$126.40	13.230%	$143.1227	$143.12	$143.10	$143.10
Purchase #5	$182.27	7.130%	$195.2659	$195.27	$195.25	$195.30
Purchase #6	$156.72	7.532%	$168.5242	$168.52	$168.50	$168.50
Purchase #7	$15.31	10.351%	$16.8947	$16.89	$16.90	$16.90
7 purchase totals =	$770.97		$835.6609	$835.66	$835.60	$835.70