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	$220.57	13.697%	$250.7815	$250.78	$250.80	$250.80
Purchase #2	$19.35	11.455%	$21.5665	$21.57	$21.55	$21.60
Purchase #3	$102.44	8.816%	$111.4711	$111.47	$111.45	$111.50
Purchase #4	$34.76	9.509%	$38.0653	$38.07	$38.05	$38.10
Purchase #5	$161.52	5.699%	$170.725	$170.73	$170.75	$170.70
Purchase #6	$156.62	9.401%	$171.3438	$171.34	$171.35	$171.30
Purchase #7	$165.34	13.560%	$187.7601	$187.76	$187.75	$187.80
7 purchase totals =	$860.60		$951.7133	$951.72	$951.70	$951.80