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	$53.71	13.337%	$60.8733	$60.87	$60.85	$60.90
Purchase #2	$113.34	4.604%	$118.5582	$118.56	$118.55	$118.60
Purchase #3	$172.79	13.490%	$196.0994	$196.10	$196.10	$196.10
Purchase #4	$185.47	3.686%	$192.3064	$192.31	$192.30	$192.30
Purchase #5	$134.56	4.670%	$140.844	$140.84	$140.85	$140.80
Purchase #6	$36.48	9.277%	$39.8642	$39.86	$39.85	$39.90
Purchase #7	$209.36	3.855%	$217.4308	$217.43	$217.45	$217.40
7 purchase totals =	$905.71		$965.9763	$965.97	$965.95	$966.00