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	$72.83	10.195%	$80.255	$80.26	$80.25	$80.30
Purchase #2	$78.32	11.536%	$87.355	$87.36	$87.35	$87.40
Purchase #3	$144.72	13.386%	$164.0922	$164.09	$164.10	$164.10
Purchase #4	$79.32	3.151%	$81.8194	$81.82	$81.80	$81.80
Purchase #5	$52.84	7.275%	$56.6841	$56.68	$56.70	$56.70
Purchase #6	$33.93	12.810%	$38.2764	$38.28	$38.30	$38.30
Purchase #7	$104.38	6.378%	$111.0374	$111.04	$111.05	$111.00
7 purchase totals =	$566.34		$619.5195	$619.53	$619.55	$619.60