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	$141.87	6.490%	$151.0774	$151.08	$151.10	$151.10
Purchase #2	$37.63	6.314%	$40.006	$40.01	$40.00	$40.00
Purchase #3	$114.41	7.546%	$123.0434	$123.04	$123.05	$123.00
Purchase #4	$112.78	4.492%	$117.8461	$117.85	$117.85	$117.80
Purchase #5	$147.90	4.174%	$154.0733	$154.07	$154.05	$154.10
Purchase #6	$74.33	9.626%	$81.485	$81.49	$81.50	$81.50
Purchase #7	$249.73	12.122%	$280.0023	$280.00	$280.00	$280.00
7 purchase totals =	$878.65		$947.5335	$947.54	$947.55	$947.50