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	$161.83	9.321%	$176.9142	$176.91	$176.90	$176.90
Purchase #2	$40.55	3.626%	$42.0203	$42.02	$42.00	$42.00
Purchase #3	$244.65	7.249%	$262.3847	$262.38	$262.40	$262.40
Purchase #4	$113.45	13.434%	$128.6909	$128.69	$128.70	$128.70
Purchase #5	$221.87	11.279%	$246.8947	$246.89	$246.90	$246.90
Purchase #6	$39.78	11.535%	$44.3686	$44.37	$44.35	$44.40
Purchase #7	$131.89	10.465%	$145.6923	$145.69	$145.70	$145.70
7 purchase totals =	$954.02		$1,046.9657	$1,046.95	$1,046.95	$1,047.00