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 $88.80   8.137%   $96.0257   $96.03   $96.05   $96.00  
  Purchase #2 $71.81   8.214%   $77.7085   $77.71   $77.70   $77.70  
  Purchase #3 $217.58   8.380%   $235.8132   $235.81   $235.80   $235.80  
  Purchase #4 $42.77   8.447%   $46.3828   $46.38   $46.40   $46.40  
  Purchase #5 $99.73   12.532%   $112.2282   $112.23   $112.25   $112.20  
  Purchase #6 $175.32   9.657%   $192.2507   $192.25   $192.25   $192.30  
  Purchase #7 $186.51   10.850%   $206.7463   $206.75   $206.75   $206.70  
  7 purchase totals = $882.52       $967.1554   $967.16   $967.20   $967.10