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	$124.78	13.602%	$141.7526	$141.75	$141.75	$141.80
Purchase #2	$29.71	12.776%	$33.5057	$33.51	$33.50	$33.50
Purchase #3	$151.87	3.193%	$156.7192	$156.72	$156.70	$156.70
Purchase #4	$20.45	8.733%	$22.2359	$22.24	$22.25	$22.20
Purchase #5	$179.54	11.615%	$200.3936	$200.39	$200.40	$200.40
Purchase #6	$225.86	12.801%	$254.7723	$254.77	$254.75	$254.80
Purchase #7	$192.46	5.229%	$202.5237	$202.52	$202.50	$202.50
7 purchase totals =	$924.67		$1,011.9030	$1,011.90	$1,011.85	$1,011.90