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 $114.69   7.127%   $122.864   $122.86   $122.85   $122.90  
  Purchase #2 $58.39   8.672%   $63.4536   $63.45   $63.45   $63.50  
  Purchase #3 $214.73   3.765%   $222.8146   $222.81   $222.80   $222.80  
  Purchase #4 $93.97   10.399%   $103.7419   $103.74   $103.75   $103.70  
  Purchase #5 $125.49   4.864%   $131.5938   $131.59   $131.60   $131.60  
  Purchase #6 $82.83   7.166%   $88.7656   $88.77   $88.75   $88.80  
  Purchase #7 $200.96   6.858%   $214.7418   $214.74   $214.75   $214.70  
  7 purchase totals = $891.06       $947.9753   $947.96   $947.95   $948.00