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	$42.64	9.387%	$46.6426	$46.64	$46.65	$46.60
Purchase #2	$93.64	10.433%	$103.4095	$103.41	$103.40	$103.40
Purchase #3	$136.35	5.154%	$143.3775	$143.38	$143.40	$143.40
Purchase #4	$11.27	6.287%	$11.9785	$11.98	$12.00	$12.00
Purchase #5	$208.49	12.312%	$234.1593	$234.16	$234.15	$234.20
Purchase #6	$187.67	11.275%	$208.8298	$208.83	$208.85	$208.80
Purchase #7	$249.86	13.223%	$282.899	$282.90	$282.90	$282.90
7 purchase totals =	$929.92		$1,031.2962	$1,031.30	$1,031.35	$1,031.30