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	$149.61	4.766%	$156.7404	$156.74	$156.75	$156.70
Purchase #2	$24.81	4.312%	$25.8798	$25.88	$25.90	$25.90
Purchase #3	$234.79	11.688%	$262.2323	$262.23	$262.25	$262.20
Purchase #4	$12.61	4.275%	$13.1491	$13.15	$13.15	$13.10
Purchase #5	$26.82	9.728%	$29.429	$29.43	$29.45	$29.40
Purchase #6	$43.86	9.242%	$47.9135	$47.91	$47.90	$47.90
Purchase #7	$59.39	5.589%	$62.7093	$62.71	$62.70	$62.70
7 purchase totals =	$551.89		$598.0534	$598.05	$598.10	$597.90