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	$33.53	8.350%	$36.3298	$36.33	$36.35	$36.30
Purchase #2	$49.49	4.102%	$51.5201	$51.52	$51.50	$51.50
Purchase #3	$111.63	13.823%	$127.0606	$127.06	$127.05	$127.10
Purchase #4	$89.30	5.126%	$93.8775	$93.88	$93.90	$93.90
Purchase #5	$235.98	10.195%	$260.0382	$260.04	$260.05	$260.00
Purchase #6	$38.29	12.414%	$43.0433	$43.04	$43.05	$43.00
Purchase #7	$58.67	11.836%	$65.6142	$65.61	$65.60	$65.60
7 purchase totals =	$616.89		$677.4837	$677.48	$677.50	$677.40