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 $185.92   8.485%   $201.6953   $201.70   $201.70   $201.70  
  Purchase #2 $161.55   6.429%   $171.936   $171.94   $171.95   $171.90  
  Purchase #3 $32.63   10.134%   $35.9367   $35.94   $35.95   $35.90  
  Purchase #4 $13.91   8.537%   $15.0975   $15.10   $15.10   $15.10  
  Purchase #5 $110.66   6.235%   $117.5597   $117.56   $117.55   $117.60  
  Purchase #6 $249.49   11.237%   $277.5252   $277.53   $277.55   $277.50  
  Purchase #7 $169.43   12.659%   $190.8781   $190.88   $190.90   $190.90  
  7 purchase totals = $923.59       $1,010.6285   $1,010.65   $1,010.70   $1,010.60