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	$99.70	5.709%	$105.3919	$105.39	$105.40	$105.40
Purchase #2	$194.45	5.258%	$204.6742	$204.67	$204.65	$204.70
Purchase #3	$245.91	11.290%	$273.6732	$273.67	$273.65	$273.70
Purchase #4	$87.91	3.255%	$90.7715	$90.77	$90.75	$90.80
Purchase #5	$245.76	6.795%	$262.4594	$262.46	$262.45	$262.50
Purchase #6	$192.54	10.392%	$212.5488	$212.55	$212.55	$212.50
Purchase #7	$205.52	8.182%	$222.3356	$222.34	$222.35	$222.30
7 purchase totals =	$1,271.79		$1,371.8546	$1,371.85	$1,371.80	$1,371.90