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	$11.90	9.348%	$13.0124	$13.01	$13.00	$13.00
Purchase #2	$55.64	4.103%	$57.9229	$57.92	$57.90	$57.90
Purchase #3	$160.27	3.261%	$165.4964	$165.50	$165.50	$165.50
Purchase #4	$194.31	13.152%	$219.8657	$219.87	$219.85	$219.90
Purchase #5	$111.66	11.568%	$124.5768	$124.58	$124.60	$124.60
Purchase #6	$200.28	10.807%	$221.9243	$221.92	$221.90	$221.90
Purchase #7	$234.52	11.233%	$260.8636	$260.86	$260.85	$260.90
7 purchase totals =	$968.58		$1,063.6621	$1,063.66	$1,063.60	$1,063.70