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	$72.37	6.476%	$77.0567	$77.06	$77.05	$77.10
Purchase #2	$103.83	8.370%	$112.5206	$112.52	$112.50	$112.50
Purchase #3	$235.96	11.844%	$263.9071	$263.91	$263.90	$263.90
Purchase #4	$55.81	13.699%	$63.4554	$63.46	$63.45	$63.50
Purchase #5	$113.95	11.103%	$126.6019	$126.60	$126.60	$126.60
Purchase #6	$186.82	13.196%	$211.4728	$211.47	$211.45	$211.50
Purchase #7	$208.95	13.176%	$236.4813	$236.48	$236.50	$236.50
7 purchase totals =	$977.69		$1,091.4958	$1,091.50	$1,091.45	$1,091.60