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	$72.79	13.583%	$82.6771	$82.68	$82.70	$82.70
Purchase #2	$138.40	4.338%	$144.4038	$144.40	$144.40	$144.40
Purchase #3	$142.78	8.181%	$154.4608	$154.46	$154.45	$154.50
Purchase #4	$79.90	13.715%	$90.8583	$90.86	$90.85	$90.90
Purchase #5	$246.64	12.719%	$278.0101	$278.01	$278.00	$278.00
Purchase #6	$175.26	12.281%	$196.7837	$196.78	$196.80	$196.80
Purchase #7	$217.42	7.232%	$233.1438	$233.14	$233.15	$233.10
7 purchase totals =	$1,073.19		$1,180.3376	$1,180.33	$1,180.35	$1,180.40