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	$200.58	11.439%	$223.5243	$223.52	$223.50	$223.50
Purchase #2	$37.89	13.466%	$42.9923	$42.99	$43.00	$43.00
Purchase #3	$98.99	11.667%	$110.5392	$110.54	$110.55	$110.50
Purchase #4	$246.66	3.447%	$255.1624	$255.16	$255.15	$255.20
Purchase #5	$51.53	12.601%	$58.0233	$58.02	$58.00	$58.00
Purchase #6	$27.87	6.102%	$29.5706	$29.57	$29.55	$29.60
Purchase #7	$200.83	13.462%	$227.8657	$227.87	$227.85	$227.90
7 purchase totals =	$864.35		$947.6778	$947.67	$947.60	$947.70