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	$177.85	10.587%	$196.679	$196.68	$196.70	$196.70
Purchase #2	$146.38	8.784%	$159.238	$159.24	$159.25	$159.20
Purchase #3	$172.28	6.583%	$183.6212	$183.62	$183.60	$183.60
Purchase #4	$184.88	8.503%	$200.6003	$200.60	$200.60	$200.60
Purchase #5	$124.88	5.378%	$131.596	$131.60	$131.60	$131.60
Purchase #6	$19.77	6.259%	$21.0074	$21.01	$21.00	$21.00
Purchase #7	$212.84	4.234%	$221.8516	$221.85	$221.85	$221.90
7 purchase totals =	$1,038.88		$1,114.5935	$1,114.60	$1,114.60	$1,114.60