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 $95.65   9.492%   $104.7291   $104.73   $104.75   $104.70  
  Purchase #2 $120.83   5.291%   $127.2231   $127.22   $127.20   $127.20  
  Purchase #3 $57.92   9.278%   $63.2938   $63.29   $63.30   $63.30  
  Purchase #4 $9.84   4.749%   $10.3073   $10.31   $10.30   $10.30  
  Purchase #5 $241.76   7.279%   $259.3577   $259.36   $259.35   $259.40  
  Purchase #6 $72.98   8.329%   $79.0585   $79.06   $79.05   $79.10  
  Purchase #7 $54.45   11.274%   $60.5887   $60.59   $60.60   $60.60  
  7 purchase totals = $653.43       $704.5582   $704.56   $704.55   $704.60