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 $196.45   9.374%   $214.8652   $214.87   $214.85   $214.90  
  Purchase #2 $166.54   7.292%   $178.6841   $178.68   $178.70   $178.70  
  Purchase #3 $149.59   6.212%   $158.8825   $158.88   $158.90   $158.90  
  Purchase #4 $133.39   3.515%   $138.0787   $138.08   $138.10   $138.10  
  Purchase #5 $234.57   11.427%   $261.3743   $261.37   $261.35   $261.40  
  Purchase #6 $41.83   8.849%   $45.5315   $45.53   $45.55   $45.50  
  Purchase #7 $25.78   5.462%   $27.1881   $27.19   $27.20   $27.20  
  7 purchase totals = $948.15       $1,024.6044   $1,024.60   $1,024.65   $1,024.70