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	$43.99	3.598%	$45.5728	$45.57	$45.55	$45.60
Purchase #2	$94.56	4.225%	$98.5552	$98.56	$98.55	$98.60
Purchase #3	$61.71	7.854%	$66.5567	$66.56	$66.55	$66.60
Purchase #4	$48.27	6.271%	$51.297	$51.30	$51.30	$51.30
Purchase #5	$212.49	11.443%	$236.8052	$236.81	$236.80	$236.80
Purchase #6	$87.96	8.609%	$95.5325	$95.53	$95.55	$95.50
Purchase #7	$212.51	13.668%	$241.5559	$241.56	$241.55	$241.60
7 purchase totals =	$761.49		$835.8753	$835.89	$835.85	$836.00