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	$200.75	8.482%	$217.7776	$217.78	$217.80	$217.80
Purchase #2	$122.78	7.749%	$132.2942	$132.29	$132.30	$132.30
Purchase #3	$77.41	3.602%	$80.1983	$80.20	$80.20	$80.20
Purchase #4	$52.59	7.476%	$56.5216	$56.52	$56.50	$56.50
Purchase #5	$136.54	8.726%	$148.4545	$148.45	$148.45	$148.50
Purchase #6	$130.54	13.743%	$148.4801	$148.48	$148.50	$148.50
Purchase #7	$181.81	4.816%	$190.566	$190.57	$190.55	$190.60
7 purchase totals =	$902.42		$974.2923	$974.29	$974.30	$974.40