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	$100.46	11.422%	$111.9345	$111.93	$111.95	$111.90
Purchase #2	$37.59	10.769%	$41.6381	$41.64	$41.65	$41.60
Purchase #3	$101.54	11.215%	$112.9277	$112.93	$112.95	$112.90
Purchase #4	$83.94	8.700%	$91.2428	$91.24	$91.25	$91.20
Purchase #5	$22.49	4.500%	$23.5021	$23.50	$23.50	$23.50
Purchase #6	$35.57	11.743%	$39.747	$39.75	$39.75	$39.70
Purchase #7	$140.75	7.776%	$151.6947	$151.69	$151.70	$151.70
7 purchase totals =	$522.34		$572.6869	$572.68	$572.75	$572.50