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	$99.59	12.156%	$111.6962	$111.70	$111.70	$111.70
Purchase #2	$107.61	13.749%	$122.4053	$122.41	$122.40	$122.40
Purchase #3	$163.92	5.353%	$172.6946	$172.69	$172.70	$172.70
Purchase #4	$187.96	4.668%	$196.734	$196.73	$196.75	$196.70
Purchase #5	$30.64	5.638%	$32.3675	$32.37	$32.35	$32.40
Purchase #6	$25.50	5.511%	$26.9053	$26.91	$26.90	$26.90
Purchase #7	$173.87	9.698%	$190.7319	$190.73	$190.75	$190.70
7 purchase totals =	$789.09		$853.5348	$853.54	$853.55	$853.50