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	$101.83	6.679%	$108.6312	$108.63	$108.65	$108.60
Purchase #2	$86.56	3.352%	$89.4615	$89.46	$89.45	$89.50
Purchase #3	$41.42	7.789%	$44.6462	$44.65	$44.65	$44.60
Purchase #4	$233.97	8.795%	$254.5477	$254.55	$254.55	$254.50
Purchase #5	$140.65	9.135%	$153.4984	$153.50	$153.50	$153.50
Purchase #6	$188.94	5.354%	$199.0558	$199.06	$199.05	$199.10
Purchase #7	$95.73	9.128%	$104.4682	$104.47	$104.45	$104.50
7 purchase totals =	$889.10		$954.3090	$954.32	$954.30	$954.30