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	$114.77	7.542%	$123.426	$123.43	$123.45	$123.40
Purchase #2	$88.81	9.328%	$97.0942	$97.09	$97.10	$97.10
Purchase #3	$45.94	10.540%	$50.7821	$50.78	$50.80	$50.80
Purchase #4	$173.52	13.168%	$196.3691	$196.37	$196.35	$196.40
Purchase #5	$241.33	3.368%	$249.458	$249.46	$249.45	$249.50
Purchase #6	$168.54	10.857%	$186.8384	$186.84	$186.85	$186.80
Purchase #7	$71.62	9.794%	$78.6345	$78.63	$78.65	$78.60
7 purchase totals =	$904.53		$982.6023	$982.60	$982.65	$982.60