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	$249.75	11.371%	$278.1491	$278.15	$278.15	$278.10
Purchase #2	$182.77	9.554%	$200.2318	$200.23	$200.25	$200.20
Purchase #3	$120.81	4.414%	$126.1426	$126.14	$126.15	$126.10
Purchase #4	$147.36	4.180%	$153.5196	$153.52	$153.50	$153.50
Purchase #5	$94.94	10.635%	$105.0369	$105.04	$105.05	$105.00
Purchase #6	$132.81	8.866%	$144.5849	$144.58	$144.60	$144.60
Purchase #7	$8.69	3.619%	$9.0045	$9.00	$9.00	$9.00
7 purchase totals =	$937.13		$1,016.6694	$1,016.66	$1,016.70	$1,016.50