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	$59.94	5.853%	$63.4483	$63.45	$63.45	$63.40
Purchase #2	$37.96	7.857%	$40.9425	$40.94	$40.95	$40.90
Purchase #3	$12.43	4.301%	$12.9646	$12.96	$12.95	$13.00
Purchase #4	$231.43	8.214%	$250.4397	$250.44	$250.45	$250.40
Purchase #5	$46.40	11.504%	$51.7379	$51.74	$51.75	$51.70
Purchase #6	$102.79	6.423%	$109.3922	$109.39	$109.40	$109.40
Purchase #7	$91.78	6.838%	$98.0559	$98.06	$98.05	$98.10
7 purchase totals =	$582.73		$626.9811	$626.98	$627.00	$626.90