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	$132.65	8.199%	$143.526	$143.53	$143.55	$143.50
Purchase #2	$122.38	11.451%	$136.3937	$136.39	$136.40	$136.40
Purchase #3	$51.66	11.359%	$57.5281	$57.53	$57.55	$57.50
Purchase #4	$151.92	5.522%	$160.309	$160.31	$160.30	$160.30
Purchase #5	$84.98	5.366%	$89.54	$89.54	$89.55	$89.50
Purchase #6	$143.93	8.485%	$156.1425	$156.14	$156.15	$156.10
Purchase #7	$179.25	13.668%	$203.7499	$203.75	$203.75	$203.70
7 purchase totals =	$866.77		$947.1892	$947.19	$947.25	$947.00