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	$83.63	9.362%	$91.4594	$91.46	$91.45	$91.50
Purchase #2	$70.48	11.684%	$78.7149	$78.71	$78.70	$78.70
Purchase #3	$162.80	4.114%	$169.4976	$169.50	$169.50	$169.50
Purchase #4	$19.49	9.485%	$21.3386	$21.34	$21.35	$21.30
Purchase #5	$21.46	10.748%	$23.7665	$23.77	$23.75	$23.80
Purchase #6	$176.57	5.596%	$186.4509	$186.45	$186.45	$186.50
Purchase #7	$99.62	11.446%	$111.0225	$111.02	$111.00	$111.00
7 purchase totals =	$634.05		$682.2504	$682.25	$682.20	$682.30