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	$40.42	6.744%	$43.1459	$43.15	$43.15	$43.10
Purchase #2	$90.35	4.540%	$94.4519	$94.45	$94.45	$94.50
Purchase #3	$227.79	13.860%	$259.3617	$259.36	$259.35	$259.40
Purchase #4	$153.75	9.798%	$168.8144	$168.81	$168.80	$168.80
Purchase #5	$56.90	11.587%	$63.493	$63.49	$63.50	$63.50
Purchase #6	$228.98	8.282%	$247.9441	$247.94	$247.95	$247.90
Purchase #7	$175.83	7.264%	$188.6023	$188.60	$188.60	$188.60
7 purchase totals =	$974.02		$1,065.8133	$1,065.80	$1,065.80	$1,065.80