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	$142.53	9.586%	$156.1929	$156.19	$156.20	$156.20
Purchase #2	$108.34	3.359%	$111.9791	$111.98	$112.00	$112.00
Purchase #3	$112.52	13.310%	$127.4964	$127.50	$127.50	$127.50
Purchase #4	$118.55	10.635%	$131.1578	$131.16	$131.15	$131.20
Purchase #5	$73.90	13.375%	$83.7841	$83.78	$83.80	$83.80
Purchase #6	$127.61	11.792%	$142.6578	$142.66	$142.65	$142.70
Purchase #7	$38.38	8.849%	$41.7762	$41.78	$41.80	$41.80
7 purchase totals =	$721.83		$795.0443	$795.05	$795.10	$795.20