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 $65.95   7.730%   $71.0479   $71.05   $71.05   $71.00  
  Purchase #2 $63.77   12.467%   $71.7202   $71.72   $71.70   $71.70  
  Purchase #3 $98.25   7.657%   $105.773   $105.77   $105.75   $105.80  
  Purchase #4 $177.80   13.728%   $202.2084   $202.21   $202.20   $202.20  
  Purchase #5 $135.68   13.786%   $154.3848   $154.38   $154.40   $154.40  
  Purchase #6 $25.50   4.512%   $26.6506   $26.65   $26.65   $26.70  
  Purchase #7 $57.38   9.154%   $62.6326   $62.63   $62.65   $62.60  
  7 purchase totals = $624.33       $694.4175   $694.41   $694.40   $694.40