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	$130.69	13.871%	$148.818	$148.82	$148.80	$148.80
Purchase #2	$154.69	9.354%	$169.1597	$169.16	$169.15	$169.20
Purchase #3	$61.50	8.652%	$66.821	$66.82	$66.80	$66.80
Purchase #4	$105.83	9.751%	$116.1495	$116.15	$116.15	$116.10
Purchase #5	$10.42	9.617%	$11.4221	$11.42	$11.40	$11.40
Purchase #6	$108.67	7.363%	$116.6714	$116.67	$116.65	$116.70
Purchase #7	$127.45	9.576%	$139.6546	$139.65	$139.65	$139.70
7 purchase totals =	$699.25		$768.6963	$768.69	$768.60	$768.70