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	$243.55	4.719%	$255.0431	$255.04	$255.05	$255.00
Purchase #2	$116.94	5.658%	$123.5565	$123.56	$123.55	$123.60
Purchase #3	$13.28	3.381%	$13.729	$13.73	$13.75	$13.70
Purchase #4	$245.39	8.237%	$265.6028	$265.60	$265.60	$265.60
Purchase #5	$192.27	7.458%	$206.6095	$206.61	$206.60	$206.60
Purchase #6	$160.36	10.861%	$177.7767	$177.78	$177.80	$177.80
Purchase #7	$90.56	9.180%	$98.8734	$98.87	$98.85	$98.90
7 purchase totals =	$1,062.35		$1,141.1910	$1,141.19	$1,141.20	$1,141.20