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	$190.48	8.380%	$206.4422	$206.44	$206.45	$206.40
Purchase #2	$184.47	11.365%	$205.435	$205.44	$205.45	$205.40
Purchase #3	$66.27	5.761%	$70.0878	$70.09	$70.10	$70.10
Purchase #4	$248.97	6.180%	$264.3563	$264.36	$264.35	$264.40
Purchase #5	$151.35	10.255%	$166.8709	$166.87	$166.85	$166.90
Purchase #6	$18.72	12.236%	$21.0106	$21.01	$21.00	$21.00
Purchase #7	$120.26	9.245%	$131.378	$131.38	$131.40	$131.40
7 purchase totals =	$980.52		$1,065.5808	$1,065.59	$1,065.60	$1,065.60