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	$231.58	5.193%	$243.6059	$243.61	$243.60	$243.60
Purchase #2	$213.44	7.847%	$230.1886	$230.19	$230.20	$230.20
Purchase #3	$184.34	13.142%	$208.566	$208.57	$208.55	$208.60
Purchase #4	$60.94	10.509%	$67.3442	$67.34	$67.35	$67.30
Purchase #5	$153.37	9.252%	$167.5598	$167.56	$167.55	$167.60
Purchase #6	$152.39	7.775%	$164.2383	$164.24	$164.25	$164.20
Purchase #7	$45.39	13.443%	$51.4918	$51.49	$51.50	$51.50
7 purchase totals =	$1,041.45		$1,132.9946	$1,133.00	$1,133.00	$1,133.00