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	$54.72	6.238%	$58.1334	$58.13	$58.15	$58.10
Purchase #2	$179.64	4.249%	$187.2729	$187.27	$187.25	$187.30
Purchase #3	$33.64	10.416%	$37.1439	$37.14	$37.15	$37.10
Purchase #4	$129.49	11.726%	$144.674	$144.67	$144.65	$144.70
Purchase #5	$39.74	10.445%	$43.8908	$43.89	$43.90	$43.90
Purchase #6	$246.76	4.664%	$258.2689	$258.27	$258.25	$258.30
Purchase #7	$209.82	6.102%	$222.6232	$222.62	$222.60	$222.60
7 purchase totals =	$893.81		$952.0071	$951.99	$951.95	$952.00