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	$22.58	13.345%	$25.5933	$25.59	$25.60	$25.60
Purchase #2	$55.55	7.743%	$59.8512	$59.85	$59.85	$59.90
Purchase #3	$244.56	9.359%	$267.4484	$267.45	$267.45	$267.40
Purchase #4	$42.86	13.477%	$48.6362	$48.64	$48.65	$48.60
Purchase #5	$50.93	9.652%	$55.8458	$55.85	$55.85	$55.80
Purchase #6	$177.45	5.482%	$187.1778	$187.18	$187.20	$187.20
Purchase #7	$100.70	13.301%	$114.0941	$114.09	$114.10	$114.10
7 purchase totals =	$694.63		$758.6468	$758.65	$758.70	$758.60