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	$42.60	9.458%	$46.6291	$46.63	$46.65	$46.60
Purchase #2	$179.91	5.450%	$189.7151	$189.72	$189.70	$189.70
Purchase #3	$97.45	12.439%	$109.5718	$109.57	$109.55	$109.60
Purchase #4	$151.64	3.110%	$156.356	$156.36	$156.35	$156.40
Purchase #5	$72.25	9.193%	$78.8919	$78.89	$78.90	$78.90
Purchase #6	$65.53	9.382%	$71.678	$71.68	$71.70	$71.70
Purchase #7	$208.61	8.536%	$226.4169	$226.42	$226.40	$226.40
7 purchase totals =	$817.99		$879.2588	$879.27	$879.25	$879.30