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	$163.89	4.530%	$171.3142	$171.31	$171.30	$171.30
Purchase #2	$194.46	10.495%	$214.8686	$214.87	$214.85	$214.90
Purchase #3	$81.85	13.240%	$92.6869	$92.69	$92.70	$92.70
Purchase #4	$105.67	5.135%	$111.0962	$111.10	$111.10	$111.10
Purchase #5	$243.52	12.699%	$274.4446	$274.44	$274.45	$274.40
Purchase #6	$104.76	6.506%	$111.5757	$111.58	$111.60	$111.60
Purchase #7	$247.88	6.707%	$264.5053	$264.51	$264.50	$264.50
7 purchase totals =	$1,142.03		$1,240.4915	$1,240.50	$1,240.50	$1,240.50