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	$163.25	5.721%	$172.5895	$172.59	$172.60	$172.60
Purchase #2	$37.86	7.837%	$40.8271	$40.83	$40.85	$40.80
Purchase #3	$176.41	4.563%	$184.4596	$184.46	$184.45	$184.50
Purchase #4	$96.57	10.462%	$106.6732	$106.67	$106.65	$106.70
Purchase #5	$141.82	12.622%	$159.7205	$159.72	$159.70	$159.70
Purchase #6	$90.85	10.486%	$100.3765	$100.38	$100.40	$100.40
Purchase #7	$6.93	8.322%	$7.5067	$7.51	$7.50	$7.50
7 purchase totals =	$713.69		$772.1531	$772.16	$772.15	$772.20