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	$205.54	9.770%	$225.6213	$225.62	$225.60	$225.60
Purchase #2	$80.42	4.109%	$83.7245	$83.72	$83.70	$83.70
Purchase #3	$57.55	4.820%	$60.3239	$60.32	$60.30	$60.30
Purchase #4	$43.49	12.868%	$49.0863	$49.09	$49.10	$49.10
Purchase #5	$20.65	10.181%	$22.7524	$22.75	$22.75	$22.80
Purchase #6	$34.85	7.693%	$37.531	$37.53	$37.55	$37.50
Purchase #7	$131.51	11.265%	$146.3246	$146.32	$146.30	$146.30
7 purchase totals =	$574.01		$625.3640	$625.35	$625.30	$625.30