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 $60.48   10.850%   $67.0421   $67.04   $67.05   $67.00  
  Purchase #2 $217.49   12.560%   $244.8067   $244.81   $244.80   $244.80  
  Purchase #3 $49.46   7.265%   $53.0533   $53.05   $53.05   $53.10  
  Purchase #4 $249.91   7.113%   $267.6861   $267.69   $267.70   $267.70  
  Purchase #5 $68.71   4.595%   $71.8672   $71.87   $71.85   $71.90  
  Purchase #6 $105.85   11.402%   $117.919   $117.92   $117.90   $117.90  
  Purchase #7 $248.71   5.280%   $261.8419   $261.84   $261.85   $261.80  
  7 purchase totals = $1,000.61       $1,084.2163   $1,084.22   $1,084.20   $1,084.20