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	$22.85	12.348%	$25.6715	$25.67	$25.65	$25.70
Purchase #2	$250.56	12.499%	$281.8775	$281.88	$281.90	$281.90
Purchase #3	$159.92	11.688%	$178.6114	$178.61	$178.60	$178.60
Purchase #4	$151.52	3.428%	$156.7141	$156.71	$156.70	$156.70
Purchase #5	$39.87	9.848%	$43.7964	$43.80	$43.80	$43.80
Purchase #6	$236.77	9.170%	$258.4818	$258.48	$258.50	$258.50
Purchase #7	$85.27	10.357%	$94.1014	$94.10	$94.10	$94.10
7 purchase totals =	$946.76		$1,039.2541	$1,039.25	$1,039.25	$1,039.30