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	$93.59	11.655%	$104.4979	$104.50	$104.50	$104.50
Purchase #2	$109.77	7.826%	$118.3606	$118.36	$118.35	$118.40
Purchase #3	$105.36	13.541%	$119.6268	$119.63	$119.65	$119.60
Purchase #4	$142.87	9.808%	$156.8827	$156.88	$156.90	$156.90
Purchase #5	$140.72	13.850%	$160.2097	$160.21	$160.20	$160.20
Purchase #6	$250.90	4.796%	$262.9332	$262.93	$262.95	$262.90
Purchase #7	$20.81	5.262%	$21.905	$21.91	$21.90	$21.90
7 purchase totals =	$864.02		$944.4159	$944.42	$944.45	$944.40