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	$82.59	3.683%	$85.6318	$85.63	$85.65	$85.60
Purchase #2	$227.37	12.448%	$255.673	$255.67	$255.65	$255.70
Purchase #3	$13.84	6.791%	$14.7799	$14.78	$14.80	$14.80
Purchase #4	$171.51	3.817%	$178.0565	$178.06	$178.05	$178.10
Purchase #5	$90.50	13.647%	$102.8505	$102.85	$102.85	$102.90
Purchase #6	$126.27	10.378%	$139.3743	$139.37	$139.35	$139.40
Purchase #7	$217.96	4.139%	$226.9814	$226.98	$227.00	$227.00
7 purchase totals =	$930.04		$1,003.3474	$1,003.34	$1,003.35	$1,003.50