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	$222.76	8.459%	$241.6033	$241.60	$241.60	$241.60
Purchase #2	$177.50	5.125%	$186.5969	$186.60	$186.60	$186.60
Purchase #3	$246.65	11.826%	$275.8188	$275.82	$275.80	$275.80
Purchase #4	$168.49	11.350%	$187.6136	$187.61	$187.60	$187.60
Purchase #5	$58.50	6.218%	$62.1375	$62.14	$62.15	$62.10
Purchase #6	$43.45	9.792%	$47.7046	$47.70	$47.70	$47.70
Purchase #7	$51.46	11.745%	$57.504	$57.50	$57.50	$57.50
7 purchase totals =	$968.81		$1,058.9787	$1,058.97	$1,058.95	$1,058.90