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	$191.72	4.719%	$200.7673	$200.77	$200.75	$200.80
Purchase #2	$35.80	6.175%	$38.0107	$38.01	$38.00	$38.00
Purchase #3	$100.80	8.832%	$109.7027	$109.70	$109.70	$109.70
Purchase #4	$75.71	8.646%	$82.2559	$82.26	$82.25	$82.30
Purchase #5	$40.25	8.382%	$43.6238	$43.62	$43.60	$43.60
Purchase #6	$52.81	9.210%	$57.6738	$57.67	$57.65	$57.70
Purchase #7	$224.31	13.817%	$255.3029	$255.30	$255.30	$255.30
7 purchase totals =	$721.40		$787.3371	$787.33	$787.25	$787.40