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	$238.38	4.724%	$249.6411	$249.64	$249.65	$249.60
Purchase #2	$87.80	4.290%	$91.5666	$91.57	$91.55	$91.60
Purchase #3	$62.28	6.811%	$66.5219	$66.52	$66.50	$66.50
Purchase #4	$139.58	10.301%	$153.9581	$153.96	$153.95	$154.00
Purchase #5	$74.89	4.682%	$78.3963	$78.40	$78.40	$78.40
Purchase #6	$125.60	9.531%	$137.5709	$137.57	$137.55	$137.60
Purchase #7	$200.55	4.667%	$209.9097	$209.91	$209.90	$209.90
7 purchase totals =	$929.08		$987.5646	$987.57	$987.50	$987.60