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	$141.69	3.108%	$146.0937	$146.09	$146.10	$146.10
Purchase #2	$202.86	7.709%	$218.4985	$218.50	$218.50	$218.50
Purchase #3	$152.52	4.215%	$158.9487	$158.95	$158.95	$158.90
Purchase #4	$30.49	6.598%	$32.5017	$32.50	$32.50	$32.50
Purchase #5	$39.35	10.189%	$43.3594	$43.36	$43.35	$43.40
Purchase #6	$101.25	3.679%	$104.975	$104.98	$105.00	$105.00
Purchase #7	$238.96	7.102%	$255.9309	$255.93	$255.95	$255.90
7 purchase totals =	$907.12		$960.3079	$960.31	$960.35	$960.30