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	$83.98	4.585%	$87.8305	$87.83	$87.85	$87.80
Purchase #2	$168.29	12.819%	$189.8631	$189.86	$189.85	$189.90
Purchase #3	$143.94	4.797%	$150.8448	$150.84	$150.85	$150.80
Purchase #4	$123.58	11.553%	$137.8572	$137.86	$137.85	$137.90
Purchase #5	$63.35	4.663%	$66.304	$66.30	$66.30	$66.30
Purchase #6	$148.66	4.542%	$155.4121	$155.41	$155.40	$155.40
Purchase #7	$51.56	9.845%	$56.6361	$56.64	$56.65	$56.60
7 purchase totals =	$783.36		$844.7478	$844.74	$844.75	$844.70