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	$133.34	8.472%	$144.6366	$144.64	$144.65	$144.60
Purchase #2	$190.28	13.487%	$215.9431	$215.94	$215.95	$215.90
Purchase #3	$121.86	12.271%	$136.8134	$136.81	$136.80	$136.80
Purchase #4	$62.53	4.866%	$65.5727	$65.57	$65.55	$65.60
Purchase #5	$46.95	10.278%	$51.7755	$51.78	$51.80	$51.80
Purchase #6	$191.30	4.619%	$200.1361	$200.14	$200.15	$200.10
Purchase #7	$130.58	13.127%	$147.7212	$147.72	$147.70	$147.70
7 purchase totals =	$876.84		$962.5986	$962.60	$962.60	$962.50