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	$155.52	4.472%	$162.4749	$162.47	$162.45	$162.50
Purchase #2	$59.62	10.806%	$66.0625	$66.06	$66.05	$66.10
Purchase #3	$183.38	12.594%	$206.4749	$206.47	$206.45	$206.50
Purchase #4	$208.33	3.193%	$214.982	$214.98	$215.00	$215.00
Purchase #5	$203.89	5.217%	$214.5269	$214.53	$214.55	$214.50
Purchase #6	$72.25	8.588%	$78.4548	$78.45	$78.45	$78.50
Purchase #7	$143.71	8.628%	$156.1093	$156.11	$156.10	$156.10
7 purchase totals =	$1,026.70		$1,099.0853	$1,099.07	$1,099.05	$1,099.20