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	$96.60	3.228%	$99.7182	$99.72	$99.70	$99.70
Purchase #2	$12.52	7.788%	$13.4951	$13.50	$13.50	$13.50
Purchase #3	$178.91	8.406%	$193.9492	$193.95	$193.95	$193.90
Purchase #4	$249.57	12.513%	$280.7987	$280.80	$280.80	$280.80
Purchase #5	$228.76	11.852%	$255.8726	$255.87	$255.85	$255.90
Purchase #6	$75.55	10.550%	$83.5205	$83.52	$83.50	$83.50
Purchase #7	$17.35	4.354%	$18.1054	$18.11	$18.10	$18.10
7 purchase totals =	$859.26		$945.4597	$945.47	$945.40	$945.40