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 $69.69   6.605%   $74.293   $74.29   $74.30   $74.30  
  Purchase #2 $250.80   4.221%   $261.3863   $261.39   $261.40   $261.40  
  Purchase #3 $116.95   12.745%   $131.8553   $131.86   $131.85   $131.90  
  Purchase #4 $249.45   9.420%   $272.9482   $272.95   $272.95   $272.90  
  Purchase #5 $96.95   13.792%   $110.3213   $110.32   $110.30   $110.30  
  Purchase #6 $242.44   7.132%   $259.7308   $259.73   $259.75   $259.70  
  Purchase #7 $228.83   8.804%   $248.9762   $248.98   $249.00   $249.00  
  7 purchase totals = $1,255.11       $1,359.5111   $1,359.52   $1,359.55   $1,359.50