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	$169.78	5.702%	$179.4609	$179.46	$179.45	$179.50
Purchase #2	$234.79	5.481%	$247.6588	$247.66	$247.65	$247.70
Purchase #3	$9.61	13.304%	$10.8885	$10.89	$10.90	$10.90
Purchase #4	$82.85	8.849%	$90.1814	$90.18	$90.20	$90.20
Purchase #5	$68.96	9.782%	$75.7057	$75.71	$75.70	$75.70
Purchase #6	$43.90	10.735%	$48.6127	$48.61	$48.60	$48.60
Purchase #7	$99.49	4.149%	$103.6178	$103.62	$103.60	$103.60
7 purchase totals =	$709.38		$756.1258	$756.13	$756.10	$756.20