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	$71.67	7.849%	$77.2954	$77.30	$77.30	$77.30
Purchase #2	$149.77	11.422%	$166.8767	$166.88	$166.90	$166.90
Purchase #3	$118.53	4.179%	$123.4834	$123.48	$123.50	$123.50
Purchase #4	$119.49	10.342%	$131.8477	$131.85	$131.85	$131.80
Purchase #5	$228.42	7.150%	$244.752	$244.75	$244.75	$244.80
Purchase #6	$155.54	5.123%	$163.5083	$163.51	$163.50	$163.50
Purchase #7	$235.43	8.666%	$255.8324	$255.83	$255.85	$255.80
7 purchase totals =	$1,078.85		$1,163.5959	$1,163.60	$1,163.65	$1,163.60