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	$172.99	3.265%	$178.6381	$178.64	$178.65	$178.60
Purchase #2	$97.93	13.859%	$111.5021	$111.50	$111.50	$111.50
Purchase #3	$82.89	10.815%	$91.8546	$91.85	$91.85	$91.90
Purchase #4	$161.47	5.821%	$170.8692	$170.87	$170.85	$170.90
Purchase #5	$196.76	13.128%	$222.5907	$222.59	$222.60	$222.60
Purchase #6	$227.86	9.656%	$249.8622	$249.86	$249.85	$249.90
Purchase #7	$23.25	8.168%	$25.1491	$25.15	$25.15	$25.10
7 purchase totals =	$963.15		$1,050.4660	$1,050.46	$1,050.45	$1,050.50