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	$39.64	8.845%	$43.1462	$43.15	$43.15	$43.10
Purchase #2	$189.35	11.288%	$210.7238	$210.72	$210.70	$210.70
Purchase #3	$62.43	8.688%	$67.8539	$67.85	$67.85	$67.90
Purchase #4	$168.98	5.329%	$177.9849	$177.98	$178.00	$178.00
Purchase #5	$132.28	7.266%	$141.8915	$141.89	$141.90	$141.90
Purchase #6	$141.44	12.381%	$158.9517	$158.95	$158.95	$159.00
Purchase #7	$156.55	10.219%	$172.5478	$172.55	$172.55	$172.50
7 purchase totals =	$890.67		$973.0998	$973.09	$973.10	$973.10