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	$241.56	9.720%	$265.0396	$265.04	$265.05	$265.00
Purchase #2	$248.72	3.434%	$257.261	$257.26	$257.25	$257.30
Purchase #3	$12.39	13.340%	$14.0428	$14.04	$14.05	$14.00
Purchase #4	$205.76	7.677%	$221.5562	$221.56	$221.55	$221.60
Purchase #5	$231.43	12.526%	$260.4189	$260.42	$260.40	$260.40
Purchase #6	$126.94	3.509%	$131.3943	$131.39	$131.40	$131.40
Purchase #7	$99.86	11.387%	$111.2311	$111.23	$111.25	$111.20
7 purchase totals =	$1,166.66		$1,260.9439	$1,260.94	$1,260.95	$1,260.90