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	$206.28	4.444%	$215.4471	$215.45	$215.45	$215.40
Purchase #2	$193.26	11.553%	$215.5873	$215.59	$215.60	$215.60
Purchase #3	$100.39	5.714%	$106.1263	$106.13	$106.15	$106.10
Purchase #4	$116.81	5.806%	$123.592	$123.59	$123.60	$123.60
Purchase #5	$129.66	8.745%	$140.9988	$141.00	$141.00	$141.00
Purchase #6	$13.45	10.224%	$14.8251	$14.83	$14.85	$14.80
Purchase #7	$177.89	10.196%	$196.0277	$196.03	$196.05	$196.00
7 purchase totals =	$937.74		$1,012.6043	$1,012.62	$1,012.70	$1,012.50