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	$171.92	4.553%	$179.7475	$179.75	$179.75	$179.70
Purchase #2	$59.58	11.533%	$66.4514	$66.45	$66.45	$66.50
Purchase #3	$12.59	7.128%	$13.4874	$13.49	$13.50	$13.50
Purchase #4	$82.74	3.843%	$85.9197	$85.92	$85.90	$85.90
Purchase #5	$177.64	10.309%	$195.9529	$195.95	$195.95	$196.00
Purchase #6	$71.38	13.715%	$81.1698	$81.17	$81.15	$81.20
Purchase #7	$136.51	4.283%	$142.3567	$142.36	$142.35	$142.40
7 purchase totals =	$712.36		$765.0854	$765.09	$765.05	$765.20