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	$22.26	10.771%	$24.6576	$24.66	$24.65	$24.70
Purchase #2	$143.31	8.498%	$155.4885	$155.49	$155.50	$155.50
Purchase #3	$108.51	3.731%	$112.5585	$112.56	$112.55	$112.60
Purchase #4	$50.54	11.844%	$56.526	$56.53	$56.55	$56.50
Purchase #5	$216.70	13.605%	$246.182	$246.18	$246.20	$246.20
Purchase #6	$59.69	13.244%	$67.5953	$67.60	$67.60	$67.60
Purchase #7	$45.51	13.125%	$51.4832	$51.48	$51.50	$51.50
7 purchase totals =	$646.52		$714.4911	$714.50	$714.55	$714.60