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	$100.46	4.328%	$104.8079	$104.81	$104.80	$104.80
Purchase #2	$239.70	10.671%	$265.2784	$265.28	$265.30	$265.30
Purchase #3	$239.36	7.293%	$256.8165	$256.82	$256.80	$256.80
Purchase #4	$66.87	8.864%	$72.7974	$72.80	$72.80	$72.80
Purchase #5	$211.50	5.109%	$222.3055	$222.31	$222.30	$222.30
Purchase #6	$32.96	6.114%	$34.9752	$34.98	$35.00	$35.00
Purchase #7	$73.72	3.368%	$76.2029	$76.20	$76.20	$76.20
7 purchase totals =	$964.57		$1,033.1838	$1,033.20	$1,033.20	$1,033.20