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	$105.83	5.287%	$111.4252	$111.43	$111.45	$111.40
Purchase #2	$89.85	7.393%	$96.4926	$96.49	$96.50	$96.50
Purchase #3	$126.99	13.399%	$144.0054	$144.01	$144.00	$144.00
Purchase #4	$78.54	8.201%	$84.9811	$84.98	$85.00	$85.00
Purchase #5	$198.71	12.265%	$223.0818	$223.08	$223.10	$223.10
Purchase #6	$208.36	11.363%	$232.0359	$232.04	$232.05	$232.00
Purchase #7	$74.66	5.102%	$78.4692	$78.47	$78.45	$78.50
7 purchase totals =	$882.94		$970.4912	$970.50	$970.55	$970.50