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	$176.64	13.640%	$200.7337	$200.73	$200.75	$200.70
Purchase #2	$178.51	8.439%	$193.5745	$193.57	$193.55	$193.60
Purchase #3	$33.82	13.627%	$38.4287	$38.43	$38.45	$38.40
Purchase #4	$118.82	4.324%	$123.9578	$123.96	$123.95	$124.00
Purchase #5	$143.26	6.323%	$152.3183	$152.32	$152.30	$152.30
Purchase #6	$128.49	12.270%	$144.2557	$144.26	$144.25	$144.30
Purchase #7	$126.95	3.256%	$131.0835	$131.08	$131.10	$131.10
7 purchase totals =	$906.49		$984.3522	$984.35	$984.35	$984.40