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	$227.98	12.475%	$256.4205	$256.42	$256.40	$256.40
Purchase #2	$73.32	11.669%	$81.8757	$81.88	$81.90	$81.90
Purchase #3	$236.75	4.804%	$248.1235	$248.12	$248.10	$248.10
Purchase #4	$112.55	13.265%	$127.4798	$127.48	$127.50	$127.50
Purchase #5	$109.59	11.852%	$122.5786	$122.58	$122.60	$122.60
Purchase #6	$17.80	4.281%	$18.562	$18.56	$18.55	$18.60
Purchase #7	$213.45	5.635%	$225.4779	$225.48	$225.50	$225.50
7 purchase totals =	$991.44		$1,080.5180	$1,080.52	$1,080.55	$1,080.60