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	$35.83	10.535%	$39.6047	$39.60	$39.60	$39.60
Purchase #2	$215.90	8.201%	$233.606	$233.61	$233.60	$233.60
Purchase #3	$238.71	3.517%	$247.1054	$247.11	$247.10	$247.10
Purchase #4	$7.77	12.387%	$8.7325	$8.73	$8.75	$8.70
Purchase #5	$239.31	6.837%	$255.6716	$255.67	$255.65	$255.70
Purchase #6	$56.83	11.772%	$63.52	$63.52	$63.50	$63.50
Purchase #7	$234.79	5.831%	$248.4806	$248.48	$248.50	$248.50
7 purchase totals =	$1,029.14		$1,096.7208	$1,096.72	$1,096.70	$1,096.70