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	$105.65	10.353%	$116.5879	$116.59	$116.60	$116.60
Purchase #2	$237.43	6.698%	$253.3331	$253.33	$253.35	$253.30
Purchase #3	$134.57	6.867%	$143.8109	$143.81	$143.80	$143.80
Purchase #4	$115.59	11.537%	$128.9256	$128.93	$128.95	$128.90
Purchase #5	$13.77	5.554%	$14.5348	$14.53	$14.55	$14.50
Purchase #6	$147.73	5.537%	$155.9098	$155.91	$155.90	$155.90
Purchase #7	$66.33	9.800%	$72.8303	$72.83	$72.85	$72.80
7 purchase totals =	$821.07		$885.9324	$885.93	$886.00	$885.80