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	$241.76	7.316%	$259.4472	$259.45	$259.45	$259.40
Purchase #2	$243.69	6.552%	$259.6566	$259.66	$259.65	$259.70
Purchase #3	$145.91	10.667%	$161.4742	$161.47	$161.45	$161.50
Purchase #4	$100.30	10.796%	$111.1284	$111.13	$111.15	$111.10
Purchase #5	$22.33	11.492%	$24.8962	$24.90	$24.90	$24.90
Purchase #6	$156.36	13.173%	$176.9573	$176.96	$176.95	$177.00
Purchase #7	$22.45	9.163%	$24.5071	$24.51	$24.50	$24.50
7 purchase totals =	$932.80		$1,018.0670	$1,018.08	$1,018.05	$1,018.10