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	$102.56	8.621%	$111.4017	$111.40	$111.40	$111.40
Purchase #2	$194.42	13.432%	$220.5345	$220.53	$220.55	$220.50
Purchase #3	$105.99	6.874%	$113.2758	$113.28	$113.30	$113.30
Purchase #4	$212.77	12.145%	$238.6109	$238.61	$238.60	$238.60
Purchase #5	$9.92	3.835%	$10.3004	$10.30	$10.30	$10.30
Purchase #6	$138.85	9.397%	$151.8977	$151.90	$151.90	$151.90
Purchase #7	$56.38	11.168%	$62.6765	$62.68	$62.70	$62.70
7 purchase totals =	$820.89		$908.6975	$908.70	$908.75	$908.70