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	$30.66	5.858%	$32.4561	$32.46	$32.45	$32.50
Purchase #2	$219.71	5.168%	$231.0646	$231.06	$231.05	$231.10
Purchase #3	$228.85	4.617%	$239.416	$239.42	$239.40	$239.40
Purchase #4	$93.59	12.187%	$104.9958	$105.00	$105.00	$105.00
Purchase #5	$73.85	3.376%	$76.3432	$76.34	$76.35	$76.30
Purchase #6	$139.50	9.644%	$152.9534	$152.95	$152.95	$153.00
Purchase #7	$165.80	8.324%	$179.6012	$179.60	$179.60	$179.60
7 purchase totals =	$951.96		$1,016.8303	$1,016.83	$1,016.80	$1,016.90