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	$62.71	10.301%	$69.1698	$69.17	$69.15	$69.20
Purchase #2	$92.59	11.664%	$103.3897	$103.39	$103.40	$103.40
Purchase #3	$23.68	5.713%	$25.0328	$25.03	$25.05	$25.00
Purchase #4	$88.73	13.673%	$100.8621	$100.86	$100.85	$100.90
Purchase #5	$78.25	9.225%	$85.4686	$85.47	$85.45	$85.50
Purchase #6	$8.40	6.686%	$8.9616	$8.96	$8.95	$9.00
Purchase #7	$101.52	11.852%	$113.5522	$113.55	$113.55	$113.60
7 purchase totals =	$455.88		$506.4368	$506.43	$506.40	$506.60