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	$238.47	4.439%	$249.0557	$249.06	$249.05	$249.10
Purchase #2	$105.77	6.705%	$112.8619	$112.86	$112.85	$112.90
Purchase #3	$43.90	12.376%	$49.3331	$49.33	$49.35	$49.30
Purchase #4	$88.34	10.289%	$97.4293	$97.43	$97.45	$97.40
Purchase #5	$86.43	4.795%	$90.5743	$90.57	$90.55	$90.60
Purchase #6	$131.81	11.418%	$146.8601	$146.86	$146.85	$146.90
Purchase #7	$107.42	6.505%	$114.4077	$114.41	$114.40	$114.40
7 purchase totals =	$802.14		$860.5221	$860.52	$860.50	$860.60