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	$80.55	13.719%	$91.6007	$91.60	$91.60	$91.60
Purchase #2	$80.65	7.509%	$86.706	$86.71	$86.70	$86.70
Purchase #3	$174.30	10.209%	$192.0943	$192.09	$192.10	$192.10
Purchase #4	$52.63	12.789%	$59.3609	$59.36	$59.35	$59.40
Purchase #5	$56.93	8.207%	$61.6022	$61.60	$61.60	$61.60
Purchase #6	$164.40	11.856%	$183.8913	$183.89	$183.90	$183.90
Purchase #7	$100.56	7.667%	$108.2699	$108.27	$108.25	$108.30
7 purchase totals =	$710.02		$783.5253	$783.52	$783.50	$783.60