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	$200.97	3.222%	$207.4453	$207.45	$207.45	$207.40
Purchase #2	$136.47	10.574%	$150.9003	$150.90	$150.90	$150.90
Purchase #3	$65.39	8.806%	$71.1482	$71.15	$71.15	$71.10
Purchase #4	$75.58	10.196%	$83.2861	$83.29	$83.30	$83.30
Purchase #5	$77.40	11.259%	$86.1145	$86.11	$86.10	$86.10
Purchase #6	$54.99	4.286%	$57.3469	$57.35	$57.35	$57.30
Purchase #7	$110.45	5.509%	$116.5347	$116.53	$116.55	$116.50
7 purchase totals =	$721.25		$772.7760	$772.78	$772.80	$772.60