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	$205.63	13.316%	$233.0117	$233.01	$233.00	$233.00
Purchase #2	$41.25	12.799%	$46.5296	$46.53	$46.55	$46.50
Purchase #3	$197.83	12.255%	$222.0741	$222.07	$222.05	$222.10
Purchase #4	$153.88	7.475%	$165.3825	$165.38	$165.40	$165.40
Purchase #5	$222.51	13.716%	$253.0295	$253.03	$253.05	$253.00
Purchase #6	$222.72	3.838%	$231.268	$231.27	$231.25	$231.30
Purchase #7	$162.82	5.180%	$171.2541	$171.25	$171.25	$171.30
7 purchase totals =	$1,206.64		$1,322.5495	$1,322.54	$1,322.55	$1,322.60