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	$105.64	6.275%	$112.2689	$112.27	$112.25	$112.30
Purchase #2	$94.89	8.700%	$103.1454	$103.15	$103.15	$103.10
Purchase #3	$241.31	7.491%	$259.3865	$259.39	$259.40	$259.40
Purchase #4	$155.51	4.330%	$162.2436	$162.24	$162.25	$162.20
Purchase #5	$155.27	12.767%	$175.0933	$175.09	$175.10	$175.10
Purchase #6	$194.34	11.758%	$217.1905	$217.19	$217.20	$217.20
Purchase #7	$35.56	6.812%	$37.9823	$37.98	$38.00	$38.00
7 purchase totals =	$982.52		$1,067.3105	$1,067.31	$1,067.35	$1,067.30