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 $58.98   5.738%   $62.3643   $62.36   $62.35   $62.40  
  Purchase #2 $248.26   5.556%   $262.0533   $262.05   $262.05   $262.10  
  Purchase #3 $9.96   9.239%   $10.8802   $10.88   $10.90   $10.90  
  Purchase #4 $20.71   7.521%   $22.2676   $22.27   $22.25   $22.30  
  Purchase #5 $237.63   3.817%   $246.7003   $246.70   $246.70   $246.70  
  Purchase #6 $48.63   11.705%   $54.3221   $54.32   $54.30   $54.30  
  Purchase #7 $78.90   9.802%   $86.6338   $86.63   $86.65   $86.60  
  7 purchase totals = $703.07       $745.2216   $745.21   $745.20   $745.30