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	$206.66	13.116%	$233.7655	$233.77	$233.75	$233.80
Purchase #2	$148.99	5.769%	$157.5852	$157.59	$157.60	$157.60
Purchase #3	$153.54	8.554%	$166.6738	$166.67	$166.65	$166.70
Purchase #4	$136.96	7.689%	$147.4909	$147.49	$147.50	$147.50
Purchase #5	$122.53	3.768%	$127.1469	$127.15	$127.15	$127.10
Purchase #6	$70.73	7.776%	$76.23	$76.23	$76.25	$76.20
Purchase #7	$158.28	11.801%	$176.9586	$176.96	$176.95	$177.00
7 purchase totals =	$997.69		$1,085.8509	$1,085.86	$1,085.85	$1,085.90