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	$80.56	6.226%	$85.5757	$85.58	$85.60	$85.60
Purchase #2	$217.48	11.731%	$242.9926	$242.99	$243.00	$243.00
Purchase #3	$19.69	5.809%	$20.8338	$20.83	$20.85	$20.80
Purchase #4	$124.50	9.291%	$136.0673	$136.07	$136.05	$136.10
Purchase #5	$87.55	9.826%	$96.1527	$96.15	$96.15	$96.20
Purchase #6	$72.72	5.358%	$76.6163	$76.62	$76.60	$76.60
Purchase #7	$83.25	3.848%	$86.4535	$86.45	$86.45	$86.50
7 purchase totals =	$685.75		$744.6919	$744.69	$744.70	$744.80