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	$148.32	12.280%	$166.5337	$166.53	$166.55	$166.50
Purchase #2	$40.58	7.592%	$43.6608	$43.66	$43.65	$43.70
Purchase #3	$87.81	3.489%	$90.8737	$90.87	$90.85	$90.90
Purchase #4	$8.95	9.242%	$9.7772	$9.78	$9.80	$9.80
Purchase #5	$46.55	13.310%	$52.7458	$52.75	$52.75	$52.70
Purchase #6	$52.78	12.770%	$59.52	$59.52	$59.50	$59.50
Purchase #7	$86.84	8.163%	$93.9287	$93.93	$93.95	$93.90
7 purchase totals =	$471.83		$517.0399	$517.04	$517.05	$517.00