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	$216.93	10.722%	$240.1892	$240.19	$240.20	$240.20
Purchase #2	$65.79	9.753%	$72.2065	$72.21	$72.20	$72.20
Purchase #3	$66.40	12.458%	$74.6721	$74.67	$74.65	$74.70
Purchase #4	$21.85	3.430%	$22.5995	$22.60	$22.60	$22.60
Purchase #5	$158.83	3.537%	$164.4478	$164.45	$164.45	$164.40
Purchase #6	$73.28	6.288%	$77.8878	$77.89	$77.90	$77.90
Purchase #7	$191.64	12.461%	$215.5203	$215.52	$215.50	$215.50
7 purchase totals =	$794.72		$867.5232	$867.53	$867.50	$867.50