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	$53.84	10.719%	$59.6111	$59.61	$59.60	$59.60
Purchase #2	$242.90	9.482%	$265.9318	$265.93	$265.95	$265.90
Purchase #3	$226.65	13.587%	$257.4449	$257.44	$257.45	$257.40
Purchase #4	$108.96	8.435%	$118.1508	$118.15	$118.15	$118.20
Purchase #5	$136.52	4.323%	$142.4218	$142.42	$142.40	$142.40
Purchase #6	$154.81	7.307%	$166.122	$166.12	$166.10	$166.10
Purchase #7	$34.81	7.273%	$37.3417	$37.34	$37.35	$37.30
7 purchase totals =	$958.49		$1,047.0241	$1,047.01	$1,047.00	$1,046.90