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	$118.72	9.816%	$130.3736	$130.37	$130.35	$130.40
Purchase #2	$209.39	10.512%	$231.4011	$231.40	$231.40	$231.40
Purchase #3	$139.86	12.538%	$157.3956	$157.40	$157.40	$157.40
Purchase #4	$11.69	5.308%	$12.3105	$12.31	$12.30	$12.30
Purchase #5	$12.50	6.369%	$13.2961	$13.30	$13.30	$13.30
Purchase #6	$151.42	6.626%	$161.4531	$161.45	$161.45	$161.50
Purchase #7	$38.39	8.424%	$41.624	$41.62	$41.60	$41.60
7 purchase totals =	$681.97		$747.8540	$747.85	$747.80	$747.90