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	$142.84	5.709%	$150.9947	$150.99	$151.00	$151.00
Purchase #2	$80.38	12.581%	$90.4926	$90.49	$90.50	$90.50
Purchase #3	$169.51	13.181%	$191.8531	$191.85	$191.85	$191.90
Purchase #4	$49.58	4.223%	$51.6738	$51.67	$51.65	$51.70
Purchase #5	$122.40	7.858%	$132.0182	$132.02	$132.00	$132.00
Purchase #6	$82.73	8.238%	$89.5453	$89.55	$89.55	$89.50
Purchase #7	$215.83	8.660%	$234.5209	$234.52	$234.50	$234.50
7 purchase totals =	$863.27		$941.0986	$941.09	$941.05	$941.10