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	$11.29	4.757%	$11.8271	$11.83	$11.85	$11.80
Purchase #2	$117.68	9.469%	$128.8231	$128.82	$128.80	$128.80
Purchase #3	$90.64	10.215%	$99.8989	$99.90	$99.90	$99.90
Purchase #4	$165.81	9.218%	$181.0944	$181.09	$181.10	$181.10
Purchase #5	$68.53	10.208%	$75.5255	$75.53	$75.55	$75.50
Purchase #6	$67.76	12.709%	$76.3716	$76.37	$76.35	$76.40
Purchase #7	$133.85	6.461%	$142.498	$142.50	$142.50	$142.50
7 purchase totals =	$655.56		$716.0386	$716.04	$716.05	$716.00