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	$206.33	4.129%	$214.8494	$214.85	$214.85	$214.80
Purchase #2	$72.98	7.304%	$78.3105	$78.31	$78.30	$78.30
Purchase #3	$125.86	10.688%	$139.3119	$139.31	$139.30	$139.30
Purchase #4	$26.74	10.382%	$29.5161	$29.52	$29.50	$29.50
Purchase #5	$46.67	4.475%	$48.7585	$48.76	$48.75	$48.80
Purchase #6	$183.40	13.469%	$208.1021	$208.10	$208.10	$208.10
Purchase #7	$155.74	13.351%	$176.5328	$176.53	$176.55	$176.50
7 purchase totals =	$817.72		$895.3813	$895.38	$895.35	$895.30