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	$107.47	5.322%	$113.1896	$113.19	$113.20	$113.20
Purchase #2	$19.91	10.844%	$22.069	$22.07	$22.05	$22.10
Purchase #3	$52.54	3.341%	$54.2954	$54.30	$54.30	$54.30
Purchase #4	$90.25	7.654%	$97.1577	$97.16	$97.15	$97.20
Purchase #5	$155.90	8.790%	$169.6036	$169.60	$169.60	$169.60
Purchase #6	$126.55	13.413%	$143.5242	$143.52	$143.50	$143.50
Purchase #7	$103.66	7.523%	$111.4583	$111.46	$111.45	$111.50
7 purchase totals =	$656.28		$711.2978	$711.30	$711.25	$711.40