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	$218.81	9.299%	$239.1571	$239.16	$239.15	$239.20
Purchase #2	$150.25	12.210%	$168.5955	$168.60	$168.60	$168.60
Purchase #3	$183.85	13.226%	$208.166	$208.17	$208.15	$208.20
Purchase #4	$53.81	11.239%	$59.8577	$59.86	$59.85	$59.90
Purchase #5	$53.56	11.314%	$59.6198	$59.62	$59.60	$59.60
Purchase #6	$113.55	11.119%	$126.1756	$126.18	$126.20	$126.20
Purchase #7	$19.38	3.377%	$20.0345	$20.03	$20.05	$20.00
7 purchase totals =	$793.21		$881.6062	$881.62	$881.60	$881.70