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	$42.60	7.664%	$45.8649	$45.86	$45.85	$45.90
Purchase #2	$122.72	7.223%	$131.5841	$131.58	$131.60	$131.60
Purchase #3	$18.62	3.856%	$19.338	$19.34	$19.35	$19.30
Purchase #4	$56.36	11.858%	$63.0432	$63.04	$63.05	$63.00
Purchase #5	$63.52	10.435%	$70.1483	$70.15	$70.15	$70.10
Purchase #6	$229.64	12.111%	$257.4517	$257.45	$257.45	$257.50
Purchase #7	$158.83	3.675%	$164.667	$164.67	$164.65	$164.70
7 purchase totals =	$692.29		$752.0972	$752.09	$752.10	$752.10