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	$127.55	8.121%	$137.9083	$137.91	$137.90	$137.90
Purchase #2	$97.26	3.382%	$100.5493	$100.55	$100.55	$100.50
Purchase #3	$47.44	8.188%	$51.3244	$51.32	$51.30	$51.30
Purchase #4	$162.74	5.747%	$172.0927	$172.09	$172.10	$172.10
Purchase #5	$44.46	4.527%	$46.4727	$46.47	$46.45	$46.50
Purchase #6	$145.63	5.315%	$153.3702	$153.37	$153.35	$153.40
Purchase #7	$200.90	4.256%	$209.4503	$209.45	$209.45	$209.50
7 purchase totals =	$825.98		$871.1679	$871.16	$871.10	$871.20