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	$204.66	13.115%	$231.5012	$231.50	$231.50	$231.50
Purchase #2	$74.82	9.778%	$82.1359	$82.14	$82.15	$82.10
Purchase #3	$182.28	8.834%	$198.3826	$198.38	$198.40	$198.40
Purchase #4	$49.40	10.291%	$54.4838	$54.48	$54.50	$54.50
Purchase #5	$240.58	9.197%	$262.7061	$262.71	$262.70	$262.70
Purchase #6	$55.33	13.170%	$62.617	$62.62	$62.60	$62.60
Purchase #7	$231.64	5.693%	$244.8273	$244.83	$244.85	$244.80
7 purchase totals =	$1,038.71		$1,136.6539	$1,136.66	$1,136.70	$1,136.60