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	$205.83	13.385%	$233.3803	$233.38	$233.40	$233.40
Purchase #2	$132.72	13.288%	$150.3558	$150.36	$150.35	$150.40
Purchase #3	$27.67	3.342%	$28.5947	$28.59	$28.60	$28.60
Purchase #4	$29.27	12.210%	$32.8439	$32.84	$32.85	$32.80
Purchase #5	$103.27	4.408%	$107.8221	$107.82	$107.80	$107.80
Purchase #6	$51.63	11.186%	$57.4053	$57.41	$57.40	$57.40
Purchase #7	$15.28	10.329%	$16.8583	$16.86	$16.85	$16.90
7 purchase totals =	$565.67		$627.2604	$627.26	$627.25	$627.30