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	$63.32	9.793%	$69.5209	$69.52	$69.50	$69.50
Purchase #2	$13.57	4.540%	$14.1861	$14.19	$14.20	$14.20
Purchase #3	$246.25	9.668%	$270.0575	$270.06	$270.05	$270.10
Purchase #4	$118.95	3.519%	$123.1359	$123.14	$123.15	$123.10
Purchase #5	$198.38	6.292%	$210.8621	$210.86	$210.85	$210.90
Purchase #6	$78.39	5.354%	$82.587	$82.59	$82.60	$82.60
Purchase #7	$249.89	3.448%	$258.5062	$258.51	$258.50	$258.50
7 purchase totals =	$968.75		$1,028.8557	$1,028.87	$1,028.85	$1,028.90