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	$116.58	3.532%	$120.6976	$120.70	$120.70	$120.70
Purchase #2	$80.36	3.452%	$83.134	$83.13	$83.15	$83.10
Purchase #3	$128.62	12.598%	$144.8235	$144.82	$144.80	$144.80
Purchase #4	$34.38	6.429%	$36.5903	$36.59	$36.60	$36.60
Purchase #5	$11.63	6.810%	$12.422	$12.42	$12.40	$12.40
Purchase #6	$88.59	7.241%	$95.0048	$95.00	$95.00	$95.00
Purchase #7	$183.66	6.834%	$196.2113	$196.21	$196.20	$196.20
7 purchase totals =	$643.82		$688.8835	$688.87	$688.85	$688.80