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	$162.33	10.646%	$179.6117	$179.61	$179.60	$179.60
Purchase #2	$65.91	12.861%	$74.3867	$74.39	$74.40	$74.40
Purchase #3	$69.78	6.664%	$74.4301	$74.43	$74.45	$74.40
Purchase #4	$162.47	3.226%	$167.7113	$167.71	$167.70	$167.70
Purchase #5	$125.98	4.672%	$131.8658	$131.87	$131.85	$131.90
Purchase #6	$111.40	6.310%	$118.4293	$118.43	$118.45	$118.40
Purchase #7	$183.87	11.273%	$204.5977	$204.60	$204.60	$204.60
7 purchase totals =	$881.74		$951.0326	$951.04	$951.05	$951.00