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	$43.32	9.262%	$47.3323	$47.33	$47.35	$47.30
Purchase #2	$50.27	8.235%	$54.4097	$54.41	$54.40	$54.40
Purchase #3	$29.46	10.306%	$32.4961	$32.50	$32.50	$32.50
Purchase #4	$139.44	9.311%	$152.4233	$152.42	$152.40	$152.40
Purchase #5	$136.95	4.610%	$143.2634	$143.26	$143.25	$143.30
Purchase #6	$169.39	10.233%	$186.7237	$186.72	$186.70	$186.70
Purchase #7	$44.58	5.316%	$46.9499	$46.95	$46.95	$46.90
7 purchase totals =	$613.41		$663.5984	$663.59	$663.55	$663.50