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	$127.29	13.381%	$144.3227	$144.32	$144.30	$144.30
Purchase #2	$46.57	4.333%	$48.5879	$48.59	$48.60	$48.60
Purchase #3	$172.72	12.812%	$194.8489	$194.85	$194.85	$194.80
Purchase #4	$124.29	11.450%	$138.5212	$138.52	$138.50	$138.50
Purchase #5	$41.75	11.382%	$46.502	$46.50	$46.50	$46.50
Purchase #6	$248.91	6.851%	$265.9628	$265.96	$265.95	$266.00
Purchase #7	$171.82	4.697%	$179.8904	$179.89	$179.90	$179.90
7 purchase totals =	$933.35		$1,018.6359	$1,018.63	$1,018.60	$1,018.60