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	$99.41	4.739%	$104.121	$104.12	$104.10	$104.10
Purchase #2	$123.47	10.222%	$136.0911	$136.09	$136.10	$136.10
Purchase #3	$160.72	13.160%	$181.8708	$181.87	$181.85	$181.90
Purchase #4	$96.72	3.813%	$100.4079	$100.41	$100.40	$100.40
Purchase #5	$132.93	8.378%	$144.0669	$144.07	$144.05	$144.10
Purchase #6	$79.60	5.836%	$84.2455	$84.25	$84.25	$84.20
Purchase #7	$111.92	4.339%	$116.7762	$116.78	$116.80	$116.80
7 purchase totals =	$804.77		$867.5794	$867.59	$867.55	$867.60