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	$11.31	5.387%	$11.9193	$11.92	$11.90	$11.90
Purchase #2	$89.98	11.559%	$100.3808	$100.38	$100.40	$100.40
Purchase #3	$33.82	4.485%	$35.3368	$35.34	$35.35	$35.30
Purchase #4	$140.57	13.614%	$159.7072	$159.71	$159.70	$159.70
Purchase #5	$74.77	10.564%	$82.6687	$82.67	$82.65	$82.70
Purchase #6	$34.55	12.564%	$38.8909	$38.89	$38.90	$38.90
Purchase #7	$86.61	10.318%	$95.5464	$95.55	$95.55	$95.50
7 purchase totals =	$471.61		$524.4501	$524.46	$524.45	$524.40