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	$230.38	6.760%	$245.9537	$245.95	$245.95	$246.00
Purchase #2	$174.53	9.230%	$190.6391	$190.64	$190.65	$190.60
Purchase #3	$152.78	13.393%	$173.2418	$173.24	$173.25	$173.20
Purchase #4	$97.86	13.520%	$111.0907	$111.09	$111.10	$111.10
Purchase #5	$148.88	5.788%	$157.4972	$157.50	$157.50	$157.50
Purchase #6	$164.64	7.242%	$176.5632	$176.56	$176.55	$176.60
Purchase #7	$152.61	7.848%	$164.5868	$164.59	$164.60	$164.60
7 purchase totals =	$1,121.68		$1,219.5725	$1,219.57	$1,219.60	$1,219.60