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	$48.53	6.207%	$51.5423	$51.54	$51.55	$51.50
Purchase #2	$176.87	3.389%	$182.8641	$182.86	$182.85	$182.90
Purchase #3	$242.88	7.854%	$261.9558	$261.96	$261.95	$262.00
Purchase #4	$10.65	9.143%	$11.6237	$11.62	$11.60	$11.60
Purchase #5	$38.56	13.250%	$43.6692	$43.67	$43.65	$43.70
Purchase #6	$31.59	4.433%	$32.9904	$32.99	$33.00	$33.00
Purchase #7	$41.52	3.290%	$42.886	$42.89	$42.90	$42.90
7 purchase totals =	$590.60		$627.5315	$627.53	$627.50	$627.60