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	$103.63	10.527%	$114.5391	$114.54	$114.55	$114.50
Purchase #2	$72.65	11.313%	$80.8689	$80.87	$80.85	$80.90
Purchase #3	$131.43	4.861%	$137.8188	$137.82	$137.80	$137.80
Purchase #4	$59.33	9.721%	$65.0975	$65.10	$65.10	$65.10
Purchase #5	$205.27	10.479%	$226.7802	$226.78	$226.80	$226.80
Purchase #6	$21.67	3.376%	$22.4016	$22.40	$22.40	$22.40
Purchase #7	$118.43	4.398%	$123.6386	$123.64	$123.65	$123.60
7 purchase totals =	$712.41		$771.1447	$771.15	$771.15	$771.10