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	$24.54	4.509%	$25.6465	$25.65	$25.65	$25.60
Purchase #2	$229.64	8.356%	$248.8287	$248.83	$248.85	$248.80
Purchase #3	$229.69	13.128%	$259.8437	$259.84	$259.85	$259.80
Purchase #4	$49.32	12.301%	$55.3869	$55.39	$55.40	$55.40
Purchase #5	$71.30	10.632%	$78.8806	$78.88	$78.90	$78.90
Purchase #6	$244.97	11.286%	$272.6173	$272.62	$272.60	$272.60
Purchase #7	$117.96	7.170%	$126.4177	$126.42	$126.40	$126.40
7 purchase totals =	$967.42		$1,067.6214	$1,067.63	$1,067.65	$1,067.50