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	$11.84	6.245%	$12.5794	$12.58	$12.60	$12.60
Purchase #2	$12.55	5.616%	$13.2548	$13.25	$13.25	$13.30
Purchase #3	$210.72	12.542%	$237.1485	$237.15	$237.15	$237.10
Purchase #4	$112.35	13.807%	$127.8622	$127.86	$127.85	$127.90
Purchase #5	$101.54	10.111%	$111.8067	$111.81	$111.80	$111.80
Purchase #6	$156.85	3.240%	$161.9319	$161.93	$161.95	$161.90
Purchase #7	$60.59	9.564%	$66.3848	$66.38	$66.40	$66.40
7 purchase totals =	$666.44		$730.9683	$730.96	$731.00	$731.00