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 $83.75   13.441%   $95.0068   $95.01   $95.00   $95.00  
  Purchase #2 $139.30   12.378%   $156.5426   $156.54   $156.55   $156.50  
  Purchase #3 $147.58   12.726%   $166.361   $166.36   $166.35   $166.40  
  Purchase #4 $86.90   3.809%   $90.21   $90.21   $90.20   $90.20  
  Purchase #5 $75.48   9.398%   $82.5736   $82.57   $82.55   $82.60  
  Purchase #6 $15.35   3.757%   $15.9267   $15.93   $15.95   $15.90  
  Purchase #7 $113.49   5.231%   $119.4267   $119.43   $119.45   $119.40  
  7 purchase totals = $661.85       $726.0474   $726.05   $726.05   $726.00