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	$41.94	3.691%	$43.488	$43.49	$43.50	$43.50
Purchase #2	$38.62	8.500%	$41.9027	$41.90	$41.90	$41.90
Purchase #3	$133.65	4.548%	$139.7284	$139.73	$139.75	$139.70
Purchase #4	$132.42	13.533%	$150.3404	$150.34	$150.35	$150.30
Purchase #5	$239.69	10.665%	$265.2529	$265.25	$265.25	$265.30
Purchase #6	$101.71	3.356%	$105.1234	$105.12	$105.10	$105.10
Purchase #7	$247.57	10.154%	$272.7083	$272.71	$272.70	$272.70
7 purchase totals =	$935.60		$1,018.5441	$1,018.54	$1,018.55	$1,018.50