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	$51.78	13.216%	$58.6232	$58.62	$58.60	$58.60
Purchase #2	$141.64	4.596%	$148.1498	$148.15	$148.15	$148.10
Purchase #3	$99.93	5.844%	$105.7699	$105.77	$105.75	$105.80
Purchase #4	$92.86	11.813%	$103.8296	$103.83	$103.85	$103.80
Purchase #5	$141.83	4.782%	$148.6123	$148.61	$148.60	$148.60
Purchase #6	$228.57	13.483%	$259.3881	$259.39	$259.40	$259.40
Purchase #7	$163.83	10.308%	$180.7176	$180.72	$180.70	$180.70
7 purchase totals =	$920.44		$1,005.0905	$1,005.09	$1,005.05	$1,005.00