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	$178.35	4.653%	$186.6486	$186.65	$186.65	$186.60
Purchase #2	$246.59	13.691%	$280.3506	$280.35	$280.35	$280.40
Purchase #3	$203.90	10.371%	$225.0465	$225.05	$225.05	$225.00
Purchase #4	$50.94	3.690%	$52.8197	$52.82	$52.80	$52.80
Purchase #5	$59.59	12.519%	$67.0501	$67.05	$67.05	$67.10
Purchase #6	$108.83	4.706%	$113.9515	$113.95	$113.95	$114.00
Purchase #7	$174.76	5.340%	$184.0922	$184.09	$184.10	$184.10
7 purchase totals =	$1,022.96		$1,109.9592	$1,109.96	$1,109.95	$1,110.00