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	$59.52	8.570%	$64.6209	$64.62	$64.60	$64.60
Purchase #2	$70.76	6.634%	$75.4542	$75.45	$75.45	$75.50
Purchase #3	$11.87	5.693%	$12.5458	$12.55	$12.55	$12.50
Purchase #4	$11.76	11.811%	$13.149	$13.15	$13.15	$13.10
Purchase #5	$27.88	12.424%	$31.3438	$31.34	$31.35	$31.30
Purchase #6	$81.97	5.188%	$86.2226	$86.22	$86.20	$86.20
Purchase #7	$194.70	11.594%	$217.2735	$217.27	$217.25	$217.30
7 purchase totals =	$458.46		$500.6098	$500.60	$500.55	$500.50