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	$225.38	3.404%	$233.0519	$233.05	$233.05	$233.10
Purchase #2	$172.72	10.453%	$190.7744	$190.77	$190.75	$190.80
Purchase #3	$62.65	6.796%	$66.9077	$66.91	$66.90	$66.90
Purchase #4	$157.72	9.213%	$172.2507	$172.25	$172.25	$172.30
Purchase #5	$66.85	11.542%	$74.5658	$74.57	$74.55	$74.60
Purchase #6	$214.70	11.671%	$239.7576	$239.76	$239.75	$239.80
Purchase #7	$198.46	8.610%	$215.5474	$215.55	$215.55	$215.50
7 purchase totals =	$1,098.48		$1,192.8555	$1,192.86	$1,192.80	$1,193.00