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	$233.99	9.584%	$256.4156	$256.42	$256.40	$256.40
Purchase #2	$37.71	4.648%	$39.4628	$39.46	$39.45	$39.50
Purchase #3	$76.85	9.644%	$84.2614	$84.26	$84.25	$84.30
Purchase #4	$73.29	6.660%	$78.1711	$78.17	$78.15	$78.20
Purchase #5	$238.71	7.424%	$256.4318	$256.43	$256.45	$256.40
Purchase #6	$163.94	7.456%	$176.1634	$176.16	$176.15	$176.20
Purchase #7	$104.64	11.253%	$116.4151	$116.42	$116.40	$116.40
7 purchase totals =	$929.13		$1,007.3212	$1,007.32	$1,007.25	$1,007.40