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	$9.68	9.188%	$10.5694	$10.57	$10.55	$10.60
Purchase #2	$83.45	3.383%	$86.2731	$86.27	$86.25	$86.30
Purchase #3	$160.97	7.303%	$172.7256	$172.73	$172.75	$172.70
Purchase #4	$84.40	6.705%	$90.059	$90.06	$90.05	$90.10
Purchase #5	$76.91	5.653%	$81.2577	$81.26	$81.25	$81.30
Purchase #6	$5.28	5.600%	$5.5757	$5.58	$5.60	$5.60
Purchase #7	$46.93	11.172%	$52.173	$52.17	$52.15	$52.20
7 purchase totals =	$467.62		$498.6335	$498.64	$498.60	$498.80