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	$132.40	9.473%	$144.9423	$144.94	$144.95	$144.90
Purchase #2	$38.85	5.437%	$40.9623	$40.96	$40.95	$41.00
Purchase #3	$127.34	10.791%	$141.0813	$141.08	$141.10	$141.10
Purchase #4	$189.52	4.656%	$198.3441	$198.34	$198.35	$198.30
Purchase #5	$123.87	6.264%	$131.6292	$131.63	$131.65	$131.60
Purchase #6	$203.98	10.169%	$224.7227	$224.72	$224.70	$224.70
Purchase #7	$12.68	6.583%	$13.5147	$13.51	$13.50	$13.50
7 purchase totals =	$828.64		$895.1966	$895.18	$895.20	$895.10