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	$173.76	6.782%	$185.5444	$185.54	$185.55	$185.50
Purchase #2	$53.83	4.772%	$56.3988	$56.40	$56.40	$56.40
Purchase #3	$68.26	11.758%	$76.286	$76.29	$76.30	$76.30
Purchase #4	$235.80	11.513%	$262.9477	$262.95	$262.95	$262.90
Purchase #5	$11.93	9.689%	$13.0859	$13.09	$13.10	$13.10
Purchase #6	$69.27	13.449%	$78.5861	$78.59	$78.60	$78.60
Purchase #7	$39.87	5.205%	$41.9452	$41.95	$41.95	$41.90
7 purchase totals =	$652.72		$714.7941	$714.81	$714.85	$714.70