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	$111.74	4.235%	$116.4722	$116.47	$116.45	$116.50
Purchase #2	$92.95	10.291%	$102.5155	$102.52	$102.50	$102.50
Purchase #3	$63.61	13.388%	$72.1261	$72.13	$72.15	$72.10
Purchase #4	$168.85	9.242%	$184.4551	$184.46	$184.45	$184.50
Purchase #5	$193.98	8.540%	$210.5459	$210.55	$210.55	$210.50
Purchase #6	$148.52	8.720%	$161.4709	$161.47	$161.45	$161.50
Purchase #7	$171.76	12.241%	$192.7851	$192.79	$192.80	$192.80
7 purchase totals =	$951.41		$1,040.3708	$1,040.39	$1,040.35	$1,040.40