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	$176.74	11.420%	$196.9237	$196.92	$196.90	$196.90
Purchase #2	$30.31	10.374%	$33.4544	$33.45	$33.45	$33.50
Purchase #3	$138.65	11.187%	$154.1608	$154.16	$154.15	$154.20
Purchase #4	$10.71	4.291%	$11.1696	$11.17	$11.15	$11.20
Purchase #5	$232.37	11.826%	$259.8501	$259.85	$259.85	$259.90
Purchase #6	$103.80	9.508%	$113.6693	$113.67	$113.65	$113.70
Purchase #7	$155.69	12.134%	$174.5814	$174.58	$174.60	$174.60
7 purchase totals =	$848.27		$943.8093	$943.80	$943.75	$944.00