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	$129.52	11.116%	$143.9174	$143.92	$143.90	$143.90
Purchase #2	$111.48	13.106%	$126.0906	$126.09	$126.10	$126.10
Purchase #3	$112.37	4.549%	$117.4817	$117.48	$117.50	$117.50
Purchase #4	$47.32	8.610%	$51.3943	$51.39	$51.40	$51.40
Purchase #5	$240.81	3.674%	$249.6574	$249.66	$249.65	$249.70
Purchase #6	$175.61	5.616%	$185.4723	$185.47	$185.45	$185.50
Purchase #7	$138.79	8.385%	$150.4275	$150.43	$150.45	$150.40
7 purchase totals =	$955.90		$1,024.4412	$1,024.44	$1,024.45	$1,024.50