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	$177.76	10.585%	$196.5759	$196.58	$196.60	$196.60
Purchase #2	$247.54	4.387%	$258.3996	$258.40	$258.40	$258.40
Purchase #3	$195.27	6.758%	$208.4663	$208.47	$208.45	$208.50
Purchase #4	$249.85	6.672%	$266.52	$266.52	$266.50	$266.50
Purchase #5	$149.34	11.481%	$166.4857	$166.49	$166.50	$166.50
Purchase #6	$202.55	7.387%	$217.5124	$217.51	$217.50	$217.50
Purchase #7	$77.60	12.676%	$87.4366	$87.44	$87.45	$87.40
7 purchase totals =	$1,299.91		$1,401.3965	$1,401.41	$1,401.40	$1,401.40