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	$114.68	3.855%	$119.1009	$119.10	$119.10	$119.10
Purchase #2	$208.52	4.389%	$217.6719	$217.67	$217.65	$217.70
Purchase #3	$100.63	10.403%	$111.0985	$111.10	$111.10	$111.10
Purchase #4	$180.50	10.731%	$199.8695	$199.87	$199.85	$199.90
Purchase #5	$171.75	6.451%	$182.8296	$182.83	$182.85	$182.80
Purchase #6	$13.87	6.809%	$14.8144	$14.81	$14.80	$14.80
Purchase #7	$5.91	9.514%	$6.4723	$6.47	$6.45	$6.50
7 purchase totals =	$795.86		$851.8571	$851.85	$851.80	$851.90