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	$44.58	4.538%	$46.603	$46.60	$46.60	$46.60
Purchase #2	$69.33	13.638%	$78.7852	$78.79	$78.80	$78.80
Purchase #3	$16.95	8.863%	$18.4523	$18.45	$18.45	$18.50
Purchase #4	$16.34	11.267%	$18.181	$18.18	$18.20	$18.20
Purchase #5	$140.94	8.852%	$153.416	$153.42	$153.40	$153.40
Purchase #6	$54.46	3.355%	$56.2871	$56.29	$56.30	$56.30
Purchase #7	$115.54	9.872%	$126.9461	$126.95	$126.95	$126.90
7 purchase totals =	$458.14		$498.6707	$498.68	$498.70	$498.70