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	$230.71	10.733%	$255.4721	$255.47	$255.45	$255.50
Purchase #2	$11.39	12.786%	$12.8463	$12.85	$12.85	$12.80
Purchase #3	$118.63	12.558%	$133.5276	$133.53	$133.55	$133.50
Purchase #4	$150.92	6.663%	$160.9758	$160.98	$161.00	$161.00
Purchase #5	$174.71	12.489%	$196.5295	$196.53	$196.55	$196.50
Purchase #6	$35.57	3.541%	$36.8295	$36.83	$36.85	$36.80
Purchase #7	$100.84	8.807%	$109.721	$109.72	$109.70	$109.70
7 purchase totals =	$822.77		$905.9018	$905.91	$905.95	$905.80