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	$208.68	3.215%	$215.3891	$215.39	$215.40	$215.40
Purchase #2	$24.48	13.746%	$27.845	$27.85	$27.85	$27.80
Purchase #3	$138.79	6.659%	$148.032	$148.03	$148.05	$148.00
Purchase #4	$71.90	9.632%	$78.8254	$78.83	$78.85	$78.80
Purchase #5	$146.96	5.814%	$155.5043	$155.50	$155.50	$155.50
Purchase #6	$245.40	8.657%	$266.6443	$266.64	$266.65	$266.60
Purchase #7	$215.90	13.526%	$245.1026	$245.10	$245.10	$245.10
7 purchase totals =	$1,052.11		$1,137.3427	$1,137.34	$1,137.40	$1,137.20