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	$243.60	8.375%	$264.0015	$264.00	$264.00	$264.00
Purchase #2	$51.67	8.682%	$56.156	$56.16	$56.15	$56.20
Purchase #3	$111.61	13.114%	$126.2465	$126.25	$126.25	$126.20
Purchase #4	$153.80	12.341%	$172.7805	$172.78	$172.80	$172.80
Purchase #5	$230.32	4.586%	$240.8825	$240.88	$240.90	$240.90
Purchase #6	$158.77	5.457%	$167.4341	$167.43	$167.45	$167.40
Purchase #7	$118.26	4.828%	$123.9696	$123.97	$123.95	$124.00
7 purchase totals =	$1,068.03		$1,151.4707	$1,151.47	$1,151.50	$1,151.50