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	$205.29	7.505%	$220.697	$220.70	$220.70	$220.70
Purchase #2	$48.96	5.154%	$51.4834	$51.48	$51.50	$51.50
Purchase #3	$225.70	11.419%	$251.4727	$251.47	$251.45	$251.50
Purchase #4	$70.51	11.610%	$78.6962	$78.70	$78.70	$78.70
Purchase #5	$41.89	6.514%	$44.6187	$44.62	$44.60	$44.60
Purchase #6	$10.94	9.466%	$11.9756	$11.98	$12.00	$12.00
Purchase #7	$80.31	11.538%	$89.5762	$89.58	$89.60	$89.60
7 purchase totals =	$683.60		$748.5198	$748.53	$748.55	$748.60