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	$168.79	4.490%	$176.3687	$176.37	$176.35	$176.40
Purchase #2	$80.62	12.787%	$90.9289	$90.93	$90.95	$90.90
Purchase #3	$164.52	4.314%	$171.6174	$171.62	$171.60	$171.60
Purchase #4	$66.66	9.687%	$73.1174	$73.12	$73.10	$73.10
Purchase #5	$11.82	3.146%	$12.1919	$12.19	$12.20	$12.20
Purchase #6	$140.89	4.838%	$147.7063	$147.71	$147.70	$147.70
Purchase #7	$139.45	11.182%	$155.0433	$155.04	$155.05	$155.00
7 purchase totals =	$772.75		$826.9739	$826.98	$826.95	$826.90