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	$196.30	13.528%	$222.8555	$222.86	$222.85	$222.90
Purchase #2	$100.37	3.210%	$103.5919	$103.59	$103.60	$103.60
Purchase #3	$101.60	4.507%	$106.1791	$106.18	$106.20	$106.20
Purchase #4	$61.67	8.453%	$66.883	$66.88	$66.90	$66.90
Purchase #5	$183.45	11.656%	$204.8329	$204.83	$204.85	$204.80
Purchase #6	$250.58	4.184%	$261.0643	$261.06	$261.05	$261.10
Purchase #7	$29.99	5.358%	$31.5969	$31.60	$31.60	$31.60
7 purchase totals =	$923.96		$997.0036	$997.00	$997.05	$997.10