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	$35.81	11.238%	$39.8343	$39.83	$39.85	$39.80
Purchase #2	$52.90	5.453%	$55.7846	$55.78	$55.80	$55.80
Purchase #3	$101.30	3.209%	$104.5507	$104.55	$104.55	$104.60
Purchase #4	$44.96	5.267%	$47.328	$47.33	$47.35	$47.30
Purchase #5	$16.59	13.863%	$18.8899	$18.89	$18.90	$18.90
Purchase #6	$48.58	10.362%	$53.6139	$53.61	$53.60	$53.60
Purchase #7	$171.29	13.271%	$194.0219	$194.02	$194.00	$194.00
7 purchase totals =	$471.43		$514.0233	$514.01	$514.05	$514.00