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	$226.31	9.362%	$247.4971	$247.50	$247.50	$247.50
Purchase #2	$15.97	6.838%	$17.062	$17.06	$17.05	$17.10
Purchase #3	$116.98	13.688%	$132.9922	$132.99	$133.00	$133.00
Purchase #4	$81.28	11.207%	$90.389	$90.39	$90.40	$90.40
Purchase #5	$50.33	8.685%	$54.7012	$54.70	$54.70	$54.70
Purchase #6	$64.62	3.538%	$66.9063	$66.91	$66.90	$66.90
Purchase #7	$99.83	11.743%	$111.553	$111.55	$111.55	$111.60
7 purchase totals =	$655.32		$721.1008	$721.10	$721.10	$721.20