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	$42.85	7.233%	$45.9493	$45.95	$45.95	$45.90
Purchase #2	$88.69	13.331%	$100.5133	$100.51	$100.50	$100.50
Purchase #3	$111.92	3.629%	$115.9816	$115.98	$116.00	$116.00
Purchase #4	$16.60	4.456%	$17.3397	$17.34	$17.35	$17.30
Purchase #5	$163.82	12.205%	$183.8142	$183.81	$183.80	$183.80
Purchase #6	$23.40	6.427%	$24.9039	$24.90	$24.90	$24.90
Purchase #7	$29.47	5.544%	$31.1038	$31.10	$31.10	$31.10
7 purchase totals =	$476.75		$519.6058	$519.59	$519.60	$519.50