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	$156.96	13.437%	$178.0507	$178.05	$178.05	$178.10
Purchase #2	$24.52	11.484%	$27.3359	$27.34	$27.35	$27.30
Purchase #3	$178.33	10.245%	$196.5999	$196.60	$196.60	$196.60
Purchase #4	$128.71	9.493%	$140.9284	$140.93	$140.95	$140.90
Purchase #5	$118.62	10.685%	$131.2945	$131.29	$131.30	$131.30
Purchase #6	$233.75	9.864%	$256.8071	$256.81	$256.80	$256.80
Purchase #7	$190.79	10.351%	$210.5387	$210.54	$210.55	$210.50
7 purchase totals =	$1,031.68		$1,141.5552	$1,141.56	$1,141.60	$1,141.50