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	$141.95	6.179%	$150.7211	$150.72	$150.70	$150.70
Purchase #2	$245.25	4.188%	$255.5211	$255.52	$255.50	$255.50
Purchase #3	$105.47	6.175%	$111.9828	$111.98	$112.00	$112.00
Purchase #4	$136.95	13.447%	$155.3657	$155.37	$155.35	$155.40
Purchase #5	$14.93	10.620%	$16.5156	$16.52	$16.50	$16.50
Purchase #6	$49.88	10.487%	$55.1109	$55.11	$55.10	$55.10
Purchase #7	$203.38	7.578%	$218.7921	$218.79	$218.80	$218.80
7 purchase totals =	$897.81		$964.0093	$964.01	$963.95	$964.00