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	$172.62	10.197%	$190.2221	$190.22	$190.20	$190.20
Purchase #2	$38.56	5.817%	$40.803	$40.80	$40.80	$40.80
Purchase #3	$226.35	3.215%	$233.6272	$233.63	$233.65	$233.60
Purchase #4	$7.77	10.567%	$8.5911	$8.59	$8.60	$8.60
Purchase #5	$199.93	11.446%	$222.814	$222.81	$222.80	$222.80
Purchase #6	$96.34	12.703%	$108.5781	$108.58	$108.60	$108.60
Purchase #7	$52.97	5.509%	$55.8881	$55.89	$55.90	$55.90
7 purchase totals =	$794.54		$860.5236	$860.52	$860.55	$860.50