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	$176.85	13.812%	$201.2765	$201.28	$201.30	$201.30
Purchase #2	$38.34	12.395%	$43.0922	$43.09	$43.10	$43.10
Purchase #3	$47.45	11.367%	$52.8436	$52.84	$52.85	$52.80
Purchase #4	$18.44	8.768%	$20.0568	$20.06	$20.05	$20.10
Purchase #5	$201.64	10.548%	$222.909	$222.91	$222.90	$222.90
Purchase #6	$40.56	11.363%	$45.1688	$45.17	$45.15	$45.20
Purchase #7	$86.69	9.862%	$95.2394	$95.24	$95.25	$95.20
7 purchase totals =	$609.97		$680.5863	$680.59	$680.60	$680.60