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	$90.37	4.767%	$94.6779	$94.68	$94.70	$94.70
Purchase #2	$183.48	3.221%	$189.3899	$189.39	$189.40	$189.40
Purchase #3	$242.55	9.354%	$265.2381	$265.24	$265.25	$265.20
Purchase #4	$18.62	3.871%	$19.3408	$19.34	$19.35	$19.30
Purchase #5	$73.46	13.605%	$83.4542	$83.45	$83.45	$83.50
Purchase #6	$66.48	8.686%	$72.2545	$72.25	$72.25	$72.30
Purchase #7	$175.47	8.278%	$189.9954	$190.00	$190.00	$190.00
7 purchase totals =	$850.43		$914.3508	$914.35	$914.40	$914.40