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	$98.32	13.234%	$111.3317	$111.33	$111.35	$111.30
Purchase #2	$118.33	11.401%	$131.8208	$131.82	$131.80	$131.80
Purchase #3	$37.80	12.839%	$42.6531	$42.65	$42.65	$42.70
Purchase #4	$133.35	4.192%	$138.94	$138.94	$138.95	$138.90
Purchase #5	$34.68	10.711%	$38.3946	$38.39	$38.40	$38.40
Purchase #6	$134.95	8.143%	$145.939	$145.94	$145.95	$145.90
Purchase #7	$115.67	5.419%	$121.9382	$121.94	$121.95	$121.90
7 purchase totals =	$673.10		$731.0174	$731.01	$731.05	$730.90