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	$68.67	5.178%	$72.2257	$72.23	$72.25	$72.20
Purchase #2	$153.49	3.301%	$158.5567	$158.56	$158.55	$158.60
Purchase #3	$30.91	11.638%	$34.5073	$34.51	$34.50	$34.50
Purchase #4	$120.60	5.695%	$127.4682	$127.47	$127.45	$127.50
Purchase #5	$212.29	7.205%	$227.5855	$227.59	$227.60	$227.60
Purchase #6	$50.74	3.619%	$52.5763	$52.58	$52.60	$52.60
Purchase #7	$15.28	12.854%	$17.2441	$17.24	$17.25	$17.20
7 purchase totals =	$651.98		$690.1638	$690.18	$690.20	$690.20