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	$122.37	7.582%	$131.6481	$131.65	$131.65	$131.60
Purchase #2	$117.68	7.246%	$126.2071	$126.21	$126.20	$126.20
Purchase #3	$247.30	13.571%	$280.8611	$280.86	$280.85	$280.90
Purchase #4	$171.64	4.654%	$179.6281	$179.63	$179.65	$179.60
Purchase #5	$180.72	9.557%	$197.9914	$197.99	$198.00	$198.00
Purchase #6	$24.38	12.153%	$27.3429	$27.34	$27.35	$27.30
Purchase #7	$69.96	3.397%	$72.3365	$72.34	$72.35	$72.30
7 purchase totals =	$934.05		$1,016.0152	$1,016.02	$1,016.05	$1,015.90