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	$219.64	6.333%	$233.5498	$233.55	$233.55	$233.50
Purchase #2	$158.98	9.803%	$174.5648	$174.56	$174.55	$174.60
Purchase #3	$76.62	11.589%	$85.4995	$85.50	$85.50	$85.50
Purchase #4	$48.61	8.754%	$52.8653	$52.87	$52.85	$52.90
Purchase #5	$111.35	13.634%	$126.5315	$126.53	$126.55	$126.50
Purchase #6	$125.93	12.784%	$142.0289	$142.03	$142.05	$142.00
Purchase #7	$83.41	5.348%	$87.8708	$87.87	$87.85	$87.90
7 purchase totals =	$824.54		$902.9106	$902.91	$902.90	$902.90