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	$124.89	7.481%	$134.233	$134.23	$134.25	$134.20
Purchase #2	$239.75	6.733%	$255.8924	$255.89	$255.90	$255.90
Purchase #3	$89.87	7.428%	$96.5455	$96.55	$96.55	$96.50
Purchase #4	$78.62	13.699%	$89.3902	$89.39	$89.40	$89.40
Purchase #5	$13.86	6.235%	$14.7242	$14.72	$14.70	$14.70
Purchase #6	$123.62	10.716%	$136.8671	$136.87	$136.85	$136.90
Purchase #7	$133.55	6.579%	$142.3363	$142.34	$142.35	$142.30
7 purchase totals =	$804.16		$869.9887	$869.99	$870.00	$869.90