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	$143.56	4.668%	$150.2614	$150.26	$150.25	$150.30
Purchase #2	$131.99	8.390%	$143.064	$143.06	$143.05	$143.10
Purchase #3	$224.35	10.201%	$247.2359	$247.24	$247.25	$247.20
Purchase #4	$179.40	11.394%	$199.8408	$199.84	$199.85	$199.80
Purchase #5	$131.89	11.340%	$146.8463	$146.85	$146.85	$146.80
Purchase #6	$214.38	6.676%	$228.692	$228.69	$228.70	$228.70
Purchase #7	$134.78	5.404%	$142.0635	$142.06	$142.05	$142.10
7 purchase totals =	$1,160.35		$1,258.0039	$1,258.00	$1,258.00	$1,258.00