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	$218.78	13.416%	$248.1315	$248.13	$248.15	$248.10
Purchase #2	$215.94	13.758%	$245.649	$245.65	$245.65	$245.60
Purchase #3	$213.32	13.720%	$242.5875	$242.59	$242.60	$242.60
Purchase #4	$116.64	5.615%	$123.1893	$123.19	$123.20	$123.20
Purchase #5	$225.88	7.318%	$242.4099	$242.41	$242.40	$242.40
Purchase #6	$189.82	3.386%	$196.2473	$196.25	$196.25	$196.20
Purchase #7	$29.27	8.725%	$31.8238	$31.82	$31.80	$31.80
7 purchase totals =	$1,209.65		$1,330.0383	$1,330.04	$1,330.05	$1,329.90