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	$126.40	10.544%	$139.7276	$139.73	$139.75	$139.70
Purchase #2	$230.39	11.276%	$256.3688	$256.37	$256.35	$256.40
Purchase #3	$56.60	12.122%	$63.4611	$63.46	$63.45	$63.50
Purchase #4	$227.68	11.272%	$253.3441	$253.34	$253.35	$253.30
Purchase #5	$121.48	12.720%	$136.9323	$136.93	$136.95	$136.90
Purchase #6	$101.60	4.291%	$105.9597	$105.96	$105.95	$106.00
Purchase #7	$54.65	8.204%	$59.1335	$59.13	$59.15	$59.10
7 purchase totals =	$918.80		$1,014.9271	$1,014.92	$1,014.95	$1,014.90