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	$171.33	6.721%	$182.8451	$182.85	$182.85	$182.80
Purchase #2	$206.97	13.208%	$234.3066	$234.31	$234.30	$234.30
Purchase #3	$82.40	10.470%	$91.0273	$91.03	$91.05	$91.00
Purchase #4	$80.82	13.243%	$91.523	$91.52	$91.50	$91.50
Purchase #5	$121.82	12.470%	$137.011	$137.01	$137.00	$137.00
Purchase #6	$26.57	5.595%	$28.0566	$28.06	$28.05	$28.10
Purchase #7	$178.67	6.680%	$190.6052	$190.61	$190.60	$190.60
7 purchase totals =	$868.58		$955.3748	$955.39	$955.35	$955.30