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	$87.78	4.310%	$91.5633	$91.56	$91.55	$91.60
Purchase #2	$20.26	3.185%	$20.9053	$20.91	$20.90	$20.90
Purchase #3	$176.57	9.162%	$192.7473	$192.75	$192.75	$192.70
Purchase #4	$159.81	5.732%	$168.9703	$168.97	$168.95	$169.00
Purchase #5	$92.80	8.159%	$100.3716	$100.37	$100.35	$100.40
Purchase #6	$7.69	3.786%	$7.9811	$7.98	$8.00	$8.00
Purchase #7	$242.90	5.140%	$255.3851	$255.39	$255.40	$255.40
7 purchase totals =	$787.81		$837.9240	$837.93	$837.90	$838.00