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	$25.39	12.711%	$28.6173	$28.62	$28.60	$28.60
Purchase #2	$136.53	4.113%	$142.1455	$142.15	$142.15	$142.10
Purchase #3	$97.96	13.828%	$111.5059	$111.51	$111.50	$111.50
Purchase #4	$134.48	3.623%	$139.3522	$139.35	$139.35	$139.40
Purchase #5	$27.40	13.483%	$31.0943	$31.09	$31.10	$31.10
Purchase #6	$72.71	6.491%	$77.4296	$77.43	$77.45	$77.40
Purchase #7	$186.94	4.874%	$196.0515	$196.05	$196.05	$196.10
7 purchase totals =	$681.41		$726.1963	$726.20	$726.20	$726.20