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	$232.94	13.514%	$264.4195	$264.42	$264.40	$264.40
Purchase #2	$48.93	5.371%	$51.558	$51.56	$51.55	$51.60
Purchase #3	$127.84	3.285%	$132.0395	$132.04	$132.05	$132.00
Purchase #4	$92.97	8.404%	$100.7832	$100.78	$100.80	$100.80
Purchase #5	$109.30	11.215%	$121.558	$121.56	$121.55	$121.60
Purchase #6	$101.80	9.727%	$111.7021	$111.70	$111.70	$111.70
Purchase #7	$43.82	10.688%	$48.5035	$48.50	$48.50	$48.50
7 purchase totals =	$757.60		$830.5638	$830.56	$830.55	$830.60