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	$59.25	9.809%	$65.0618	$65.06	$65.05	$65.10
Purchase #2	$55.78	6.487%	$59.3984	$59.40	$59.40	$59.40
Purchase #3	$242.83	7.426%	$260.8626	$260.86	$260.85	$260.90
Purchase #4	$108.75	7.103%	$116.4745	$116.47	$116.45	$116.50
Purchase #5	$230.69	3.659%	$239.1309	$239.13	$239.15	$239.10
Purchase #6	$73.74	4.862%	$77.3252	$77.33	$77.35	$77.30
Purchase #7	$104.25	5.862%	$110.3611	$110.36	$110.35	$110.40
7 purchase totals =	$875.29		$928.6145	$928.61	$928.60	$928.70