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	$40.38	10.633%	$44.6736	$44.67	$44.65	$44.70
Purchase #2	$37.30	8.291%	$40.3925	$40.39	$40.40	$40.40
Purchase #3	$116.70	5.630%	$123.2702	$123.27	$123.25	$123.30
Purchase #4	$49.72	11.130%	$55.2538	$55.25	$55.25	$55.30
Purchase #5	$63.48	5.614%	$67.0438	$67.04	$67.05	$67.00
Purchase #6	$240.83	7.834%	$259.6966	$259.70	$259.70	$259.70
Purchase #7	$87.71	7.715%	$94.4768	$94.48	$94.50	$94.50
7 purchase totals =	$636.12		$684.8073	$684.80	$684.80	$684.90