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	$107.39	10.396%	$118.5543	$118.55	$118.55	$118.60
Purchase #2	$157.61	13.533%	$178.9394	$178.94	$178.95	$178.90
Purchase #3	$198.95	13.543%	$225.8938	$225.89	$225.90	$225.90
Purchase #4	$236.96	5.476%	$249.9359	$249.94	$249.95	$249.90
Purchase #5	$151.62	10.156%	$167.0185	$167.02	$167.00	$167.00
Purchase #6	$107.55	3.785%	$111.6208	$111.62	$111.60	$111.60
Purchase #7	$71.81	4.243%	$74.8569	$74.86	$74.85	$74.90
7 purchase totals =	$1,031.89		$1,126.8196	$1,126.82	$1,126.80	$1,126.80