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	$76.75	12.357%	$86.234	$86.23	$86.25	$86.20
Purchase #2	$47.29	8.550%	$51.3333	$51.33	$51.35	$51.30
Purchase #3	$166.39	3.794%	$172.7028	$172.70	$172.70	$172.70
Purchase #4	$31.25	8.182%	$33.8069	$33.81	$33.80	$33.80
Purchase #5	$99.42	4.510%	$103.9038	$103.90	$103.90	$103.90
Purchase #6	$44.70	8.807%	$48.6367	$48.64	$48.65	$48.60
Purchase #7	$110.29	8.333%	$119.4805	$119.48	$119.50	$119.50
7 purchase totals =	$576.09		$616.0980	$616.09	$616.15	$616.00