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	$112.32	8.353%	$121.7021	$121.70	$121.70	$121.70
Purchase #2	$184.60	13.460%	$209.4472	$209.45	$209.45	$209.40
Purchase #3	$179.42	6.209%	$190.5602	$190.56	$190.55	$190.60
Purchase #4	$19.46	11.177%	$21.635	$21.64	$21.65	$21.60
Purchase #5	$94.52	6.784%	$100.9322	$100.93	$100.95	$100.90
Purchase #6	$112.43	3.204%	$116.0323	$116.03	$116.05	$116.00
Purchase #7	$100.68	11.704%	$112.4636	$112.46	$112.45	$112.50
7 purchase totals =	$803.43		$872.7726	$872.77	$872.80	$872.70