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	$228.80	8.132%	$247.406	$247.41	$247.40	$247.40
Purchase #2	$111.26	7.544%	$119.6535	$119.65	$119.65	$119.70
Purchase #3	$199.38	8.289%	$215.9066	$215.91	$215.90	$215.90
Purchase #4	$100.98	10.446%	$111.5284	$111.53	$111.55	$111.50
Purchase #5	$81.82	11.710%	$91.4011	$91.40	$91.40	$91.40
Purchase #6	$137.43	12.684%	$154.8616	$154.86	$154.85	$154.90
Purchase #7	$124.47	5.597%	$131.4366	$131.44	$131.45	$131.40
7 purchase totals =	$984.14		$1,072.1938	$1,072.20	$1,072.20	$1,072.20