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	$113.37	9.741%	$124.4134	$124.41	$124.40	$124.40
Purchase #2	$131.83	6.700%	$140.6626	$140.66	$140.65	$140.70
Purchase #3	$63.80	12.733%	$71.9237	$71.92	$71.90	$71.90
Purchase #4	$116.76	9.400%	$127.7354	$127.74	$127.75	$127.70
Purchase #5	$190.94	4.197%	$198.9538	$198.95	$198.95	$199.00
Purchase #6	$73.83	3.628%	$76.5086	$76.51	$76.50	$76.50
Purchase #7	$226.85	13.234%	$256.8713	$256.87	$256.85	$256.90
7 purchase totals =	$917.38		$997.0688	$997.06	$997.00	$997.10