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	$126.96	13.319%	$143.8698	$143.87	$143.85	$143.90
Purchase #2	$204.63	13.153%	$231.545	$231.55	$231.55	$231.50
Purchase #3	$233.55	13.686%	$265.5137	$265.51	$265.50	$265.50
Purchase #4	$172.47	7.602%	$185.5812	$185.58	$185.60	$185.60
Purchase #5	$78.84	5.247%	$82.9767	$82.98	$83.00	$83.00
Purchase #6	$145.66	3.874%	$151.3029	$151.30	$151.30	$151.30
Purchase #7	$185.72	12.271%	$208.5097	$208.51	$208.50	$208.50
7 purchase totals =	$1,147.83		$1,269.2990	$1,269.30	$1,269.30	$1,269.30