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	$127.39	8.162%	$137.7876	$137.79	$137.80	$137.80
Purchase #2	$170.72	12.321%	$191.7544	$191.75	$191.75	$191.80
Purchase #3	$217.64	3.121%	$224.4325	$224.43	$224.45	$224.40
Purchase #4	$78.83	9.710%	$86.4844	$86.48	$86.50	$86.50
Purchase #5	$128.35	13.284%	$145.4	$145.40	$145.40	$145.40
Purchase #6	$139.99	11.274%	$155.7725	$155.77	$155.75	$155.80
Purchase #7	$104.82	11.562%	$116.9393	$116.94	$116.95	$116.90
7 purchase totals =	$967.74		$1,058.5707	$1,058.56	$1,058.60	$1,058.60