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 $98.32   7.661%   $105.8523   $105.85   $105.85   $105.90  
  Purchase #2 $230.29   13.413%   $261.1788   $261.18   $261.20   $261.20  
  Purchase #3 $100.48   5.204%   $105.709   $105.71   $105.70   $105.70  
  Purchase #4 $156.56   6.717%   $167.0761   $167.08   $167.10   $167.10  
  Purchase #5 $31.55   12.336%   $35.442   $35.44   $35.45   $35.40  
  Purchase #6 $43.77   12.108%   $49.0697   $49.07   $49.05   $49.10  
  Purchase #7 $11.41   10.405%   $12.5972   $12.60   $12.60   $12.60  
  7 purchase totals = $672.38       $736.9251   $736.93   $736.95   $737.00