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	$69.60	9.381%	$76.1292	$76.13	$76.15	$76.10
Purchase #2	$171.63	4.111%	$178.6857	$178.69	$178.70	$178.70
Purchase #3	$95.69	11.178%	$106.3862	$106.39	$106.40	$106.40
Purchase #4	$61.72	13.495%	$70.0491	$70.05	$70.05	$70.00
Purchase #5	$59.72	4.792%	$62.5818	$62.58	$62.60	$62.60
Purchase #6	$55.28	8.429%	$59.9396	$59.94	$59.95	$59.90
Purchase #7	$207.95	4.521%	$217.3514	$217.35	$217.35	$217.40
7 purchase totals =	$721.59		$771.1230	$771.13	$771.20	$771.10