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	$103.45	8.143%	$111.8739	$111.87	$111.85	$111.90
Purchase #2	$123.39	6.245%	$131.0957	$131.10	$131.10	$131.10
Purchase #3	$104.57	12.625%	$117.772	$117.77	$117.75	$117.80
Purchase #4	$112.83	10.185%	$124.3217	$124.32	$124.30	$124.30
Purchase #5	$232.36	12.508%	$261.4236	$261.42	$261.40	$261.40
Purchase #6	$184.91	10.688%	$204.6732	$204.67	$204.65	$204.70
Purchase #7	$245.78	8.138%	$265.7816	$265.78	$265.80	$265.80
7 purchase totals =	$1,107.29		$1,216.9417	$1,216.93	$1,216.85	$1,217.00