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 $65.36   5.662%   $69.0607   $69.06   $69.05   $69.10  
  Purchase #2 $240.61   8.810%   $261.8077   $261.81   $261.80   $261.80  
  Purchase #3 $95.72   9.532%   $104.844   $104.84   $104.85   $104.80  
  Purchase #4 $47.84   10.715%   $52.9661   $52.97   $52.95   $53.00  
  Purchase #5 $95.65   8.811%   $104.0777   $104.08   $104.10   $104.10  
  Purchase #6 $34.46   3.771%   $35.7595   $35.76   $35.75   $35.80  
  Purchase #7 $233.97   8.648%   $254.2037   $254.20   $254.20   $254.20  
  7 purchase totals = $813.61       $882.7194   $882.72   $882.70   $882.80