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	$41.49	5.380%	$43.7222	$43.72	$43.70	$43.70
Purchase #2	$130.69	4.679%	$136.805	$136.81	$136.80	$136.80
Purchase #3	$168.80	3.745%	$175.1216	$175.12	$175.10	$175.10
Purchase #4	$91.66	8.772%	$99.7004	$99.70	$99.70	$99.70
Purchase #5	$241.77	6.131%	$256.5929	$256.59	$256.60	$256.60
Purchase #6	$95.45	9.492%	$104.5101	$104.51	$104.50	$104.50
Purchase #7	$90.96	13.683%	$103.4061	$103.41	$103.40	$103.40
7 purchase totals =	$860.82		$919.8583	$919.86	$919.80	$919.80