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	$43.33	7.209%	$46.4537	$46.45	$46.45	$46.50
Purchase #2	$11.84	5.808%	$12.5277	$12.53	$12.55	$12.50
Purchase #3	$154.93	10.554%	$171.2813	$171.28	$171.30	$171.30
Purchase #4	$231.72	3.135%	$238.9844	$238.98	$239.00	$239.00
Purchase #5	$206.83	7.567%	$222.4808	$222.48	$222.50	$222.50
Purchase #6	$85.81	5.304%	$90.3614	$90.36	$90.35	$90.40
Purchase #7	$59.29	4.734%	$62.0968	$62.10	$62.10	$62.10
7 purchase totals =	$793.75		$844.1861	$844.18	$844.25	$844.30