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	$119.71	5.706%	$126.5407	$126.54	$126.55	$126.50
Purchase #2	$88.35	10.524%	$97.648	$97.65	$97.65	$97.60
Purchase #3	$88.97	12.518%	$100.1073	$100.11	$100.10	$100.10
Purchase #4	$237.86	7.724%	$256.2323	$256.23	$256.25	$256.20
Purchase #5	$139.93	7.564%	$150.5143	$150.51	$150.50	$150.50
Purchase #6	$242.54	12.831%	$273.6603	$273.66	$273.65	$273.70
Purchase #7	$61.45	10.330%	$67.7978	$67.80	$67.80	$67.80
7 purchase totals =	$978.81		$1,072.5007	$1,072.50	$1,072.50	$1,072.40