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	$145.35	13.145%	$164.4563	$164.46	$164.45	$164.50
Purchase #2	$113.76	13.280%	$128.8673	$128.87	$128.85	$128.90
Purchase #3	$69.47	13.652%	$78.954	$78.95	$78.95	$79.00
Purchase #4	$31.32	10.227%	$34.5231	$34.52	$34.50	$34.50
Purchase #5	$171.67	13.555%	$194.9399	$194.94	$194.95	$194.90
Purchase #6	$96.45	12.509%	$108.5149	$108.51	$108.50	$108.50
Purchase #7	$221.28	9.377%	$242.0294	$242.03	$242.05	$242.00
7 purchase totals =	$849.30		$952.2849	$952.28	$952.25	$952.30