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	$137.97	4.320%	$143.9303	$143.93	$143.95	$143.90
Purchase #2	$194.63	3.108%	$200.6791	$200.68	$200.70	$200.70
Purchase #3	$80.94	11.493%	$90.2424	$90.24	$90.25	$90.20
Purchase #4	$29.85	6.727%	$31.858	$31.86	$31.85	$31.90
Purchase #5	$221.66	4.321%	$231.2379	$231.24	$231.25	$231.20
Purchase #6	$81.93	13.380%	$92.8922	$92.89	$92.90	$92.90
Purchase #7	$223.49	12.319%	$251.0217	$251.02	$251.00	$251.00
7 purchase totals =	$970.47		$1,041.8616	$1,041.86	$1,041.90	$1,041.80