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	$123.32	5.301%	$129.8572	$129.86	$129.85	$129.90
Purchase #2	$146.27	3.143%	$150.8673	$150.87	$150.85	$150.90
Purchase #3	$141.86	10.169%	$156.2857	$156.29	$156.30	$156.30
Purchase #4	$215.83	3.104%	$222.5294	$222.53	$222.55	$222.50
Purchase #5	$92.63	10.844%	$102.6748	$102.67	$102.65	$102.70
Purchase #6	$126.63	10.264%	$139.6273	$139.63	$139.65	$139.60
Purchase #7	$107.49	8.491%	$116.617	$116.62	$116.60	$116.60
7 purchase totals =	$954.03		$1,018.4587	$1,018.47	$1,018.45	$1,018.50