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 $61.72   11.822%   $69.0165   $69.02   $69.00   $69.00  
  Purchase #2 $146.92   7.332%   $157.6922   $157.69   $157.70   $157.70  
  Purchase #3 $44.59   6.188%   $47.3492   $47.35   $47.35   $47.30  
  Purchase #4 $157.58   8.835%   $171.5022   $171.50   $171.50   $171.50  
  Purchase #5 $48.61   11.131%   $54.0208   $54.02   $54.00   $54.00  
  Purchase #6 $35.28   11.127%   $39.2056   $39.21   $39.20   $39.20  
  Purchase #7 $168.97   10.801%   $187.2204   $187.22   $187.20   $187.20  
  7 purchase totals = $663.67       $726.0069   $726.01   $725.95   $725.90