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	$157.97	9.444%	$172.8887	$172.89	$172.90	$172.90
Purchase #2	$161.92	8.447%	$175.5974	$175.60	$175.60	$175.60
Purchase #3	$145.90	4.768%	$152.8565	$152.86	$152.85	$152.90
Purchase #4	$101.77	9.496%	$111.4341	$111.43	$111.45	$111.40
Purchase #5	$69.90	9.107%	$76.2658	$76.27	$76.25	$76.30
Purchase #6	$190.25	7.653%	$204.8098	$204.81	$204.80	$204.80
Purchase #7	$161.43	8.507%	$175.1629	$175.16	$175.15	$175.20
7 purchase totals =	$989.14		$1,069.0152	$1,069.02	$1,069.00	$1,069.10