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	$208.30	3.531%	$215.6551	$215.66	$215.65	$215.70
Purchase #2	$153.76	10.316%	$169.6219	$169.62	$169.60	$169.60
Purchase #3	$143.68	5.154%	$151.0853	$151.09	$151.10	$151.10
Purchase #4	$15.85	12.233%	$17.7889	$17.79	$17.80	$17.80
Purchase #5	$111.31	3.619%	$115.3383	$115.34	$115.35	$115.30
Purchase #6	$189.89	3.307%	$196.1697	$196.17	$196.15	$196.20
Purchase #7	$35.40	5.847%	$37.4698	$37.47	$37.45	$37.50
7 purchase totals =	$858.19		$903.1290	$903.14	$903.10	$903.20