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	$104.50	4.105%	$108.7897	$108.79	$108.80	$108.80
Purchase #2	$116.81	10.328%	$128.8741	$128.87	$128.85	$128.90
Purchase #3	$85.86	6.574%	$91.5044	$91.50	$91.50	$91.50
Purchase #4	$38.98	11.475%	$43.453	$43.45	$43.45	$43.50
Purchase #5	$222.99	9.448%	$244.0581	$244.06	$244.05	$244.10
Purchase #6	$215.45	6.654%	$229.786	$229.79	$229.80	$229.80
Purchase #7	$93.48	12.758%	$105.4062	$105.41	$105.40	$105.40
7 purchase totals =	$878.07		$951.8715	$951.87	$951.85	$952.00