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	$65.59	8.699%	$71.2957	$71.30	$71.30	$71.30
Purchase #2	$208.56	4.255%	$217.4342	$217.43	$217.45	$217.40
Purchase #3	$86.70	10.815%	$96.0766	$96.08	$96.10	$96.10
Purchase #4	$11.95	12.870%	$13.488	$13.49	$13.50	$13.50
Purchase #5	$70.36	10.620%	$77.8322	$77.83	$77.85	$77.80
Purchase #6	$165.44	10.524%	$182.8509	$182.85	$182.85	$182.90
Purchase #7	$80.25	6.509%	$85.4735	$85.47	$85.45	$85.50
7 purchase totals =	$688.85		$744.4511	$744.45	$744.50	$744.50