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	$64.56	8.746%	$70.2064	$70.21	$70.20	$70.20
Purchase #2	$168.25	5.345%	$177.243	$177.24	$177.25	$177.20
Purchase #3	$13.60	4.283%	$14.1825	$14.18	$14.20	$14.20
Purchase #4	$98.34	13.767%	$111.8785	$111.88	$111.90	$111.90
Purchase #5	$17.60	9.664%	$19.3009	$19.30	$19.30	$19.30
Purchase #6	$105.53	3.850%	$109.5929	$109.59	$109.60	$109.60
Purchase #7	$190.64	13.577%	$216.5232	$216.52	$216.50	$216.50
7 purchase totals =	$658.52		$718.9274	$718.92	$718.95	$718.90