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	$113.74	12.742%	$128.2328	$128.23	$128.25	$128.20
Purchase #2	$148.36	12.737%	$167.2566	$167.26	$167.25	$167.30
Purchase #3	$208.45	3.401%	$215.5394	$215.54	$215.55	$215.50
Purchase #4	$149.78	13.837%	$170.5051	$170.51	$170.50	$170.50
Purchase #5	$126.29	4.197%	$131.5904	$131.59	$131.60	$131.60
Purchase #6	$127.75	10.400%	$141.036	$141.04	$141.05	$141.00
Purchase #7	$212.30	5.526%	$224.0317	$224.03	$224.05	$224.00
7 purchase totals =	$1,086.67		$1,178.1920	$1,178.20	$1,178.25	$1,178.10