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	$62.42	4.762%	$65.3924	$65.39	$65.40	$65.40
Purchase #2	$107.32	3.818%	$111.4175	$111.42	$111.40	$111.40
Purchase #3	$19.34	12.856%	$21.8264	$21.83	$21.85	$21.80
Purchase #4	$210.81	7.600%	$226.8316	$226.83	$226.85	$226.80
Purchase #5	$92.52	7.427%	$99.3915	$99.39	$99.40	$99.40
Purchase #6	$73.91	12.355%	$83.0416	$83.04	$83.05	$83.00
Purchase #7	$233.38	9.597%	$255.7775	$255.78	$255.80	$255.80
7 purchase totals =	$799.70		$863.6785	$863.68	$863.75	$863.60