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	$95.77	6.770%	$102.2536	$102.25	$102.25	$102.30
Purchase #2	$239.79	10.713%	$265.4787	$265.48	$265.50	$265.50
Purchase #3	$199.43	10.226%	$219.8237	$219.82	$219.80	$219.80
Purchase #4	$176.64	12.267%	$198.3084	$198.31	$198.30	$198.30
Purchase #5	$231.76	11.533%	$258.4889	$258.49	$258.50	$258.50
Purchase #6	$5.79	8.727%	$6.2953	$6.30	$6.30	$6.30
Purchase #7	$10.51	3.305%	$10.8574	$10.86	$10.85	$10.90
7 purchase totals =	$959.69		$1,061.5060	$1,061.51	$1,061.50	$1,061.60