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	$235.30	8.646%	$255.644	$255.64	$255.65	$255.60
Purchase #2	$74.35	10.374%	$82.0631	$82.06	$82.05	$82.10
Purchase #3	$123.96	10.219%	$136.6275	$136.63	$136.65	$136.60
Purchase #4	$29.80	4.186%	$31.0474	$31.05	$31.05	$31.00
Purchase #5	$177.28	9.628%	$194.3485	$194.35	$194.35	$194.30
Purchase #6	$49.78	5.363%	$52.4497	$52.45	$52.45	$52.40
Purchase #7	$179.81	6.130%	$190.8324	$190.83	$190.85	$190.80
7 purchase totals =	$870.28		$943.0126	$943.01	$943.05	$942.80