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	$59.56	10.759%	$65.9681	$65.97	$65.95	$66.00
Purchase #2	$183.79	11.751%	$205.3872	$205.39	$205.40	$205.40
Purchase #3	$151.63	13.520%	$172.1304	$172.13	$172.15	$172.10
Purchase #4	$55.32	10.415%	$61.0816	$61.08	$61.10	$61.10
Purchase #5	$131.94	5.494%	$139.1888	$139.19	$139.20	$139.20
Purchase #6	$18.81	5.457%	$19.8365	$19.84	$19.85	$19.80
Purchase #7	$134.86	11.573%	$150.4673	$150.47	$150.45	$150.50
7 purchase totals =	$735.91		$814.0599	$814.07	$814.10	$814.10