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	$112.65	9.810%	$123.701	$123.70	$123.70	$123.70
Purchase #2	$245.85	12.483%	$276.5395	$276.54	$276.55	$276.50
Purchase #3	$81.38	10.359%	$89.8102	$89.81	$89.80	$89.80
Purchase #4	$118.68	9.619%	$130.0958	$130.10	$130.10	$130.10
Purchase #5	$72.90	10.804%	$80.7761	$80.78	$80.80	$80.80
Purchase #6	$136.94	8.266%	$148.2595	$148.26	$148.25	$148.30
Purchase #7	$190.61	12.688%	$214.7946	$214.79	$214.80	$214.80
7 purchase totals =	$959.01		$1,063.9767	$1,063.98	$1,064.00	$1,064.00