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	$74.57	9.376%	$81.5617	$81.56	$81.55	$81.60
Purchase #2	$151.46	3.633%	$156.9625	$156.96	$156.95	$157.00
Purchase #3	$248.39	12.110%	$278.47	$278.47	$278.45	$278.50
Purchase #4	$140.51	4.134%	$146.3187	$146.32	$146.30	$146.30
Purchase #5	$98.80	12.520%	$111.1698	$111.17	$111.15	$111.20
Purchase #6	$127.75	5.346%	$134.5795	$134.58	$134.60	$134.60
Purchase #7	$137.58	12.275%	$154.4679	$154.47	$154.45	$154.50
7 purchase totals =	$979.06		$1,063.5301	$1,063.53	$1,063.45	$1,063.70