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	$86.49	10.517%	$95.5862	$95.59	$95.60	$95.60
Purchase #2	$40.90	6.291%	$43.473	$43.47	$43.45	$43.50
Purchase #3	$69.28	13.511%	$78.6404	$78.64	$78.65	$78.60
Purchase #4	$121.50	11.694%	$135.7082	$135.71	$135.70	$135.70
Purchase #5	$14.89	4.149%	$15.5078	$15.51	$15.50	$15.50
Purchase #6	$139.73	6.157%	$148.3332	$148.33	$148.35	$148.30
Purchase #7	$144.45	9.853%	$158.6827	$158.68	$158.70	$158.70
7 purchase totals =	$617.24		$675.9315	$675.93	$675.95	$675.90