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	$172.94	9.196%	$188.8436	$188.84	$188.85	$188.80
Purchase #2	$219.26	3.772%	$227.5305	$227.53	$227.55	$227.50
Purchase #3	$223.67	3.656%	$231.8474	$231.85	$231.85	$231.80
Purchase #4	$182.68	7.377%	$196.1563	$196.16	$196.15	$196.20
Purchase #5	$92.81	13.794%	$105.6122	$105.61	$105.60	$105.60
Purchase #6	$105.89	5.570%	$111.7881	$111.79	$111.80	$111.80
Purchase #7	$233.41	3.128%	$240.7111	$240.71	$240.70	$240.70
7 purchase totals =	$1,230.66		$1,302.4892	$1,302.49	$1,302.50	$1,302.40