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	$205.64	13.155%	$232.6919	$232.69	$232.70	$232.70
Purchase #2	$33.58	8.638%	$36.4806	$36.48	$36.50	$36.50
Purchase #3	$122.83	4.768%	$128.6865	$128.69	$128.70	$128.70
Purchase #4	$50.57	6.254%	$53.7326	$53.73	$53.75	$53.70
Purchase #5	$78.88	6.392%	$83.922	$83.92	$83.90	$83.90
Purchase #6	$231.41	11.690%	$258.4618	$258.46	$258.45	$258.50
Purchase #7	$224.84	13.612%	$255.4452	$255.45	$255.45	$255.40
7 purchase totals =	$947.75		$1,049.4206	$1,049.42	$1,049.45	$1,049.40