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	$196.39	9.453%	$214.9547	$214.95	$214.95	$215.00
Purchase #2	$40.78	13.862%	$46.4329	$46.43	$46.45	$46.40
Purchase #3	$38.55	5.423%	$40.6406	$40.64	$40.65	$40.60
Purchase #4	$231.52	8.672%	$251.5974	$251.60	$251.60	$251.60
Purchase #5	$218.64	9.273%	$238.9145	$238.91	$238.90	$238.90
Purchase #6	$15.39	3.277%	$15.8943	$15.89	$15.90	$15.90
Purchase #7	$97.73	5.864%	$103.4609	$103.46	$103.45	$103.50
7 purchase totals =	$839.00		$911.8953	$911.88	$911.90	$911.90