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	$245.67	6.488%	$261.6091	$261.61	$261.60	$261.60
Purchase #2	$140.71	4.410%	$146.9153	$146.92	$146.90	$146.90
Purchase #3	$24.29	7.426%	$26.0938	$26.09	$26.10	$26.10
Purchase #4	$245.88	4.471%	$256.8733	$256.87	$256.85	$256.90
Purchase #5	$242.66	5.517%	$256.0476	$256.05	$256.05	$256.00
Purchase #6	$19.56	5.868%	$20.7078	$20.71	$20.70	$20.70
Purchase #7	$37.31	8.347%	$40.4243	$40.42	$40.40	$40.40
7 purchase totals =	$956.08		$1,008.6712	$1,008.67	$1,008.60	$1,008.60