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	$119.69	10.196%	$131.8936	$131.89	$131.90	$131.90
Purchase #2	$103.85	10.638%	$114.8976	$114.90	$114.90	$114.90
Purchase #3	$68.29	9.611%	$74.8534	$74.85	$74.85	$74.90
Purchase #4	$36.98	4.115%	$38.5017	$38.50	$38.50	$38.50
Purchase #5	$125.71	4.813%	$131.7604	$131.76	$131.75	$131.80
Purchase #6	$203.45	4.543%	$212.6927	$212.69	$212.70	$212.70
Purchase #7	$226.95	13.855%	$258.3939	$258.39	$258.40	$258.40
7 purchase totals =	$884.92		$962.9933	$962.98	$963.00	$963.10