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	$143.47	8.698%	$155.949	$155.95	$155.95	$155.90
Purchase #2	$206.53	4.335%	$215.4831	$215.48	$215.50	$215.50
Purchase #3	$216.83	13.269%	$245.6012	$245.60	$245.60	$245.60
Purchase #4	$93.56	4.762%	$98.0153	$98.02	$98.00	$98.00
Purchase #5	$20.57	3.795%	$21.3506	$21.35	$21.35	$21.40
Purchase #6	$225.65	4.538%	$235.89	$235.89	$235.90	$235.90
Purchase #7	$61.47	8.492%	$66.69	$66.69	$66.70	$66.70
7 purchase totals =	$968.08		$1,038.9792	$1,038.98	$1,039.00	$1,039.00