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	$200.90	11.442%	$223.887	$223.89	$223.90	$223.90
Purchase #2	$184.29	5.766%	$194.9162	$194.92	$194.90	$194.90
Purchase #3	$244.51	9.176%	$266.9462	$266.95	$266.95	$266.90
Purchase #4	$24.69	5.159%	$25.9638	$25.96	$25.95	$26.00
Purchase #5	$182.29	4.715%	$190.885	$190.89	$190.90	$190.90
Purchase #6	$112.39	9.356%	$122.9052	$122.91	$122.90	$122.90
Purchase #7	$133.57	4.498%	$139.578	$139.58	$139.60	$139.60
7 purchase totals =	$1,082.64		$1,165.0814	$1,165.10	$1,165.10	$1,165.10