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	$123.45	7.139%	$132.2631	$132.26	$132.25	$132.30
Purchase #2	$106.35	4.825%	$111.4814	$111.48	$111.50	$111.50
Purchase #3	$51.64	13.270%	$58.4926	$58.49	$58.50	$58.50
Purchase #4	$71.85	6.603%	$76.5943	$76.59	$76.60	$76.60
Purchase #5	$246.32	3.127%	$254.0224	$254.02	$254.00	$254.00
Purchase #6	$112.39	10.750%	$124.4719	$124.47	$124.45	$124.50
Purchase #7	$6.52	10.415%	$7.1991	$7.20	$7.20	$7.20
7 purchase totals =	$718.52		$764.5248	$764.51	$764.50	$764.60