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	$148.90	9.192%	$162.5869	$162.59	$162.60	$162.60
Purchase #2	$189.63	8.704%	$206.1354	$206.14	$206.15	$206.10
Purchase #3	$48.40	8.361%	$52.4467	$52.45	$52.45	$52.40
Purchase #4	$37.54	11.504%	$41.8586	$41.86	$41.85	$41.90
Purchase #5	$116.98	12.485%	$131.585	$131.59	$131.60	$131.60
Purchase #6	$217.53	11.422%	$242.3763	$242.38	$242.40	$242.40
Purchase #7	$56.91	6.561%	$60.6439	$60.64	$60.65	$60.60
7 purchase totals =	$815.89		$897.6328	$897.65	$897.70	$897.60