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	$247.29	3.688%	$256.4101	$256.41	$256.40	$256.40
Purchase #2	$34.70	8.480%	$37.6426	$37.64	$37.65	$37.60
Purchase #3	$242.84	7.296%	$260.5576	$260.56	$260.55	$260.60
Purchase #4	$198.43	3.257%	$204.8929	$204.89	$204.90	$204.90
Purchase #5	$242.34	5.603%	$255.9183	$255.92	$255.90	$255.90
Purchase #6	$18.87	10.742%	$20.897	$20.90	$20.90	$20.90
Purchase #7	$105.42	6.448%	$112.2175	$112.22	$112.20	$112.20
7 purchase totals =	$1,089.89		$1,148.5360	$1,148.54	$1,148.50	$1,148.50