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 $69.46   6.815%   $74.1937   $74.19   $74.20   $74.20  
  Purchase #2 $152.43   8.252%   $165.0085   $165.01   $165.00   $165.00  
  Purchase #3 $62.54   3.480%   $64.7164   $64.72   $64.70   $64.70  
  Purchase #4 $207.49   9.859%   $227.9464   $227.95   $227.95   $227.90  
  Purchase #5 $235.64   6.425%   $250.7799   $250.78   $250.80   $250.80  
  Purchase #6 $189.35   10.493%   $209.2185   $209.22   $209.20   $209.20  
  Purchase #7 $17.78   7.708%   $19.1505   $19.15   $19.15   $19.20  
  7 purchase totals = $934.69       $1,011.0139   $1,011.02   $1,011.00   $1,011.00