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	$231.25	10.517%	$255.5706	$255.57	$255.55	$255.60
Purchase #2	$46.59	9.601%	$51.0631	$51.06	$51.05	$51.10
Purchase #3	$19.45	6.771%	$20.767	$20.77	$20.75	$20.80
Purchase #4	$116.77	4.790%	$122.3633	$122.36	$122.35	$122.40
Purchase #5	$100.89	4.109%	$105.0356	$105.04	$105.05	$105.00
Purchase #6	$104.94	3.732%	$108.8564	$108.86	$108.85	$108.90
Purchase #7	$57.73	8.763%	$62.7889	$62.79	$62.80	$62.80
7 purchase totals =	$677.62		$726.4449	$726.45	$726.40	$726.60