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	$232.72	3.733%	$241.4074	$241.41	$241.40	$241.40
Purchase #2	$244.71	11.367%	$272.5262	$272.53	$272.55	$272.50
Purchase #3	$111.38	13.580%	$126.5054	$126.51	$126.50	$126.50
Purchase #4	$126.80	12.173%	$142.2354	$142.24	$142.25	$142.20
Purchase #5	$152.43	4.163%	$158.7757	$158.78	$158.80	$158.80
Purchase #6	$245.65	12.443%	$276.2162	$276.22	$276.20	$276.20
Purchase #7	$133.89	5.566%	$141.3423	$141.34	$141.35	$141.30
7 purchase totals =	$1,247.58		$1,359.0086	$1,359.03	$1,359.05	$1,358.90