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	$39.44	10.834%	$43.7129	$43.71	$43.70	$43.70
Purchase #2	$163.59	11.721%	$182.7644	$182.76	$182.75	$182.80
Purchase #3	$131.97	3.874%	$137.0825	$137.08	$137.10	$137.10
Purchase #4	$70.62	3.462%	$73.0649	$73.06	$73.05	$73.10
Purchase #5	$30.85	11.624%	$34.436	$34.44	$34.45	$34.40
Purchase #6	$33.83	7.328%	$36.3091	$36.31	$36.30	$36.30
Purchase #7	$18.31	11.746%	$20.4607	$20.46	$20.45	$20.50
7 purchase totals =	$488.61		$527.8305	$527.82	$527.80	$527.90