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	$21.57	3.628%	$22.3526	$22.35	$22.35	$22.40
Purchase #2	$11.94	10.330%	$13.1734	$13.17	$13.15	$13.20
Purchase #3	$205.61	9.873%	$225.9099	$225.91	$225.90	$225.90
Purchase #4	$177.40	13.174%	$200.7707	$200.77	$200.75	$200.80
Purchase #5	$20.33	3.358%	$21.0127	$21.01	$21.00	$21.00
Purchase #6	$194.77	10.417%	$215.0592	$215.06	$215.05	$215.10
Purchase #7	$22.56	13.429%	$25.5896	$25.59	$25.60	$25.60
7 purchase totals =	$654.18		$723.8681	$723.86	$723.80	$724.00