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	$186.66	7.500%	$200.6595	$200.66	$200.65	$200.70
Purchase #2	$175.90	13.705%	$200.0071	$200.01	$200.00	$200.00
Purchase #3	$71.38	9.472%	$78.1411	$78.14	$78.15	$78.10
Purchase #4	$117.94	7.264%	$126.5072	$126.51	$126.50	$126.50
Purchase #5	$16.32	12.399%	$18.3435	$18.34	$18.35	$18.30
Purchase #6	$198.72	9.503%	$217.6044	$217.60	$217.60	$217.60
Purchase #7	$37.66	10.210%	$41.5051	$41.51	$41.50	$41.50
7 purchase totals =	$804.58		$882.7679	$882.77	$882.75	$882.70