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	$238.79	6.646%	$254.66	$254.66	$254.65	$254.70
Purchase #2	$13.55	10.286%	$14.9438	$14.94	$14.95	$14.90
Purchase #3	$194.75	11.724%	$217.5825	$217.58	$217.60	$217.60
Purchase #4	$25.32	13.837%	$28.8235	$28.82	$28.80	$28.80
Purchase #5	$228.95	12.285%	$257.0765	$257.08	$257.10	$257.10
Purchase #6	$51.67	9.312%	$56.4815	$56.48	$56.50	$56.50
Purchase #7	$100.53	11.302%	$111.8919	$111.89	$111.90	$111.90
7 purchase totals =	$853.56		$941.4597	$941.45	$941.50	$941.50