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	$142.86	7.435%	$153.4816	$153.48	$153.50	$153.50
Purchase #2	$131.89	7.477%	$141.7514	$141.75	$141.75	$141.80
Purchase #3	$19.38	8.472%	$21.0219	$21.02	$21.00	$21.00
Purchase #4	$29.52	11.493%	$32.9127	$32.91	$32.90	$32.90
Purchase #5	$164.67	7.785%	$177.4896	$177.49	$177.50	$177.50
Purchase #6	$142.98	5.330%	$150.6008	$150.60	$150.60	$150.60
Purchase #7	$210.56	11.743%	$235.2861	$235.29	$235.30	$235.30
7 purchase totals =	$841.86		$912.5441	$912.54	$912.55	$912.60