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	$69.61	4.235%	$72.558	$72.56	$72.55	$72.60
Purchase #2	$122.94	13.189%	$139.1546	$139.15	$139.15	$139.20
Purchase #3	$220.50	3.759%	$228.7886	$228.79	$228.80	$228.80
Purchase #4	$75.52	13.105%	$85.4169	$85.42	$85.40	$85.40
Purchase #5	$178.79	12.293%	$200.7687	$200.77	$200.75	$200.80
Purchase #6	$241.49	8.248%	$261.4081	$261.41	$261.40	$261.40
Purchase #7	$198.62	11.845%	$222.1465	$222.15	$222.15	$222.10
7 purchase totals =	$1,107.47		$1,210.2414	$1,210.25	$1,210.20	$1,210.30