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	$9.67	9.461%	$10.5849	$10.58	$10.60	$10.60
Purchase #2	$38.68	12.684%	$43.5862	$43.59	$43.60	$43.60
Purchase #3	$20.89	10.672%	$23.1194	$23.12	$23.10	$23.10
Purchase #4	$55.63	3.857%	$57.7756	$57.78	$57.80	$57.80
Purchase #5	$78.37	10.805%	$86.8379	$86.84	$86.85	$86.80
Purchase #6	$68.89	10.739%	$76.2881	$76.29	$76.30	$76.30
Purchase #7	$7.89	12.333%	$8.8631	$8.86	$8.85	$8.90
7 purchase totals =	$280.02		$307.0552	$307.06	$307.10	$307.10