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	$243.56	4.189%	$253.7627	$253.76	$253.75	$253.80
Purchase #2	$137.32	9.612%	$150.5192	$150.52	$150.50	$150.50
Purchase #3	$47.51	11.278%	$52.8682	$52.87	$52.85	$52.90
Purchase #4	$132.31	5.754%	$139.9231	$139.92	$139.90	$139.90
Purchase #5	$59.61	8.644%	$64.7627	$64.76	$64.75	$64.80
Purchase #6	$12.76	3.373%	$13.1904	$13.19	$13.20	$13.20
Purchase #7	$231.31	4.488%	$241.6912	$241.69	$241.70	$241.70
7 purchase totals =	$864.38		$916.7175	$916.71	$916.65	$916.80