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	$138.59	10.813%	$153.5757	$153.58	$153.60	$153.60
Purchase #2	$176.49	11.530%	$196.8393	$196.84	$196.85	$196.80
Purchase #3	$173.62	6.447%	$184.8133	$184.81	$184.80	$184.80
Purchase #4	$47.95	3.421%	$49.5904	$49.59	$49.60	$49.60
Purchase #5	$162.32	10.140%	$178.7792	$178.78	$178.80	$178.80
Purchase #6	$142.77	4.293%	$148.8991	$148.90	$148.90	$148.90
Purchase #7	$74.82	13.567%	$84.9708	$84.97	$84.95	$85.00
7 purchase totals =	$916.56		$997.4678	$997.47	$997.50	$997.50