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	$197.52	6.797%	$210.9454	$210.95	$210.95	$210.90
Purchase #2	$104.34	12.714%	$117.6058	$117.61	$117.60	$117.60
Purchase #3	$40.35	8.735%	$43.8746	$43.87	$43.85	$43.90
Purchase #4	$11.38	12.509%	$12.8035	$12.80	$12.80	$12.80
Purchase #5	$96.26	4.394%	$100.4897	$100.49	$100.50	$100.50
Purchase #6	$237.50	7.564%	$255.4645	$255.46	$255.45	$255.50
Purchase #7	$95.76	5.478%	$101.0057	$101.01	$101.00	$101.00
7 purchase totals =	$783.11		$842.1892	$842.19	$842.15	$842.20