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	$128.79	10.141%	$141.8506	$141.85	$141.85	$141.90
Purchase #2	$150.43	12.320%	$168.963	$168.96	$168.95	$169.00
Purchase #3	$13.67	8.292%	$14.8035	$14.80	$14.80	$14.80
Purchase #4	$38.78	9.608%	$42.506	$42.51	$42.50	$42.50
Purchase #5	$72.38	13.376%	$82.0615	$82.06	$82.05	$82.10
Purchase #6	$51.99	6.275%	$55.2524	$55.25	$55.25	$55.30
Purchase #7	$113.25	9.336%	$123.823	$123.82	$123.80	$123.80
7 purchase totals =	$569.29		$629.2600	$629.25	$629.20	$629.40