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	$54.62	12.679%	$61.5453	$61.55	$61.55	$61.50
Purchase #2	$112.55	12.716%	$126.8619	$126.86	$126.85	$126.90
Purchase #3	$211.98	7.367%	$227.5966	$227.60	$227.60	$227.60
Purchase #4	$13.58	4.390%	$14.1762	$14.18	$14.20	$14.20
Purchase #5	$228.80	5.874%	$242.2397	$242.24	$242.25	$242.20
Purchase #6	$104.51	6.660%	$111.4704	$111.47	$111.45	$111.50
Purchase #7	$58.48	3.316%	$60.4192	$60.42	$60.40	$60.40
7 purchase totals =	$784.52		$844.3093	$844.32	$844.30	$844.30