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	$57.46	8.429%	$62.3033	$62.30	$62.30	$62.30
Purchase #2	$80.29	13.189%	$90.8794	$90.88	$90.90	$90.90
Purchase #3	$92.47	7.511%	$99.4154	$99.42	$99.40	$99.40
Purchase #4	$151.91	12.183%	$170.4172	$170.42	$170.40	$170.40
Purchase #5	$65.98	7.195%	$70.7273	$70.73	$70.75	$70.70
Purchase #6	$197.93	10.484%	$218.681	$218.68	$218.70	$218.70
Purchase #7	$235.55	11.622%	$262.9256	$262.93	$262.95	$262.90
7 purchase totals =	$881.59		$975.3492	$975.36	$975.40	$975.30