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 $183.79   9.135%   $200.5792   $200.58   $200.60   $200.60  
  Purchase #2 $216.36   11.255%   $240.7113   $240.71   $240.70   $240.70  
  Purchase #3 $85.86   12.645%   $96.717   $96.72   $96.70   $96.70  
  Purchase #4 $117.73   6.477%   $125.3554   $125.36   $125.35   $125.40  
  Purchase #5 $169.72   8.397%   $183.9714   $183.97   $183.95   $184.00  
  Purchase #6 $164.27   9.529%   $179.9233   $179.92   $179.90   $179.90  
  Purchase #7 $125.81   12.657%   $141.7338   $141.73   $141.75   $141.70  
  7 purchase totals = $1,063.54       $1,168.9914   $1,168.99   $1,168.95   $1,169.00