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	$86.27	10.622%	$95.4336	$95.43	$95.45	$95.40
Purchase #2	$52.57	8.719%	$57.1536	$57.15	$57.15	$57.20
Purchase #3	$41.33	13.609%	$46.9546	$46.95	$46.95	$47.00
Purchase #4	$94.61	9.491%	$103.5894	$103.59	$103.60	$103.60
Purchase #5	$20.30	7.632%	$21.8493	$21.85	$21.85	$21.80
Purchase #6	$11.57	8.779%	$12.5857	$12.59	$12.60	$12.60
Purchase #7	$110.82	6.443%	$117.9601	$117.96	$117.95	$118.00
7 purchase totals =	$417.47		$455.5263	$455.52	$455.55	$455.60