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	$149.29	13.584%	$169.5696	$169.57	$169.55	$169.60
Purchase #2	$95.43	9.429%	$104.4281	$104.43	$104.45	$104.40
Purchase #3	$124.63	5.463%	$131.4385	$131.44	$131.45	$131.40
Purchase #4	$128.56	8.522%	$139.5159	$139.52	$139.50	$139.50
Purchase #5	$37.56	9.317%	$41.0595	$41.06	$41.05	$41.10
Purchase #6	$148.28	7.195%	$158.9487	$158.95	$158.95	$158.90
Purchase #7	$15.44	7.442%	$16.589	$16.59	$16.60	$16.60
7 purchase totals =	$699.19		$761.5493	$761.56	$761.55	$761.50