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	$39.41	10.643%	$43.6044	$43.60	$43.60	$43.60
Purchase #2	$212.37	12.469%	$238.8504	$238.85	$238.85	$238.90
Purchase #3	$72.94	13.538%	$82.8146	$82.81	$82.80	$82.80
Purchase #4	$15.73	3.793%	$16.3266	$16.33	$16.35	$16.30
Purchase #5	$176.93	11.723%	$197.6715	$197.67	$197.65	$197.70
Purchase #6	$198.96	9.743%	$218.3447	$218.34	$218.35	$218.30
Purchase #7	$71.25	9.849%	$78.2674	$78.27	$78.25	$78.30
7 purchase totals =	$787.59		$875.8796	$875.87	$875.85	$875.90