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	$59.96	3.794%	$62.2349	$62.23	$62.25	$62.20
Purchase #2	$55.33	12.873%	$62.4526	$62.45	$62.45	$62.50
Purchase #3	$219.95	7.215%	$235.8194	$235.82	$235.80	$235.80
Purchase #4	$56.91	8.727%	$61.8765	$61.88	$61.90	$61.90
Purchase #5	$42.71	7.506%	$45.9158	$45.92	$45.90	$45.90
Purchase #6	$105.71	10.635%	$116.9523	$116.95	$116.95	$117.00
Purchase #7	$155.45	10.434%	$171.6697	$171.67	$171.65	$171.70
7 purchase totals =	$696.02		$756.9212	$756.92	$756.90	$757.00