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	$233.59	8.457%	$253.3447	$253.34	$253.35	$253.30
Purchase #2	$129.39	7.240%	$138.7578	$138.76	$138.75	$138.80
Purchase #3	$75.86	13.713%	$86.2627	$86.26	$86.25	$86.30
Purchase #4	$248.83	13.536%	$282.5116	$282.51	$282.50	$282.50
Purchase #5	$215.49	3.403%	$222.8231	$222.82	$222.80	$222.80
Purchase #6	$81.38	5.218%	$85.6264	$85.63	$85.65	$85.60
Purchase #7	$44.47	6.268%	$47.2574	$47.26	$47.25	$47.30
7 purchase totals =	$1,029.01		$1,116.5837	$1,116.58	$1,116.55	$1,116.60