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	$238.67	8.499%	$258.9546	$258.95	$258.95	$259.00
Purchase #2	$236.35	11.246%	$262.9299	$262.93	$262.95	$262.90
Purchase #3	$112.40	13.425%	$127.4897	$127.49	$127.50	$127.50
Purchase #4	$38.51	12.110%	$43.1736	$43.17	$43.15	$43.20
Purchase #5	$13.38	3.370%	$13.8309	$13.83	$13.85	$13.80
Purchase #6	$143.85	5.581%	$151.8783	$151.88	$151.90	$151.90
Purchase #7	$177.82	12.592%	$200.2111	$200.21	$200.20	$200.20
7 purchase totals =	$960.98		$1,058.4681	$1,058.46	$1,058.50	$1,058.50