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	$224.87	3.316%	$232.3267	$232.33	$232.35	$232.30
Purchase #2	$128.55	3.168%	$132.6225	$132.62	$132.60	$132.60
Purchase #3	$137.72	5.330%	$145.0605	$145.06	$145.05	$145.10
Purchase #4	$153.26	12.782%	$172.8497	$172.85	$172.85	$172.80
Purchase #5	$120.70	12.831%	$136.187	$136.19	$136.20	$136.20
Purchase #6	$55.70	3.264%	$57.518	$57.52	$57.50	$57.50
Purchase #7	$138.52	3.423%	$143.2615	$143.26	$143.25	$143.30
7 purchase totals =	$959.32		$1,019.8259	$1,019.83	$1,019.80	$1,019.80