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	$119.66	9.855%	$131.4525	$131.45	$131.45	$131.50
Purchase #2	$119.57	4.161%	$124.5453	$124.55	$124.55	$124.50
Purchase #3	$105.25	6.785%	$112.3912	$112.39	$112.40	$112.40
Purchase #4	$164.99	3.316%	$170.4611	$170.46	$170.45	$170.50
Purchase #5	$247.53	12.623%	$278.7757	$278.78	$278.80	$278.80
Purchase #6	$59.38	8.591%	$64.4813	$64.48	$64.50	$64.50
Purchase #7	$35.62	12.413%	$40.0415	$40.04	$40.05	$40.00
7 purchase totals =	$852.00		$922.1486	$922.15	$922.20	$922.20