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	$124.82	5.488%	$131.6701	$131.67	$131.65	$131.70
Purchase #2	$139.90	12.866%	$157.8995	$157.90	$157.90	$157.90
Purchase #3	$19.45	12.608%	$21.9023	$21.90	$21.90	$21.90
Purchase #4	$242.65	8.264%	$262.7026	$262.70	$262.70	$262.70
Purchase #5	$57.48	3.193%	$59.3153	$59.32	$59.30	$59.30
Purchase #6	$213.57	5.617%	$225.5662	$225.57	$225.55	$225.60
Purchase #7	$95.48	5.446%	$100.6798	$100.68	$100.70	$100.70
7 purchase totals =	$893.35		$959.7358	$959.74	$959.70	$959.80