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 $235.60   13.605%   $267.6534   $267.65   $267.65   $267.70  
  Purchase #2 $82.34   12.529%   $92.6564   $92.66   $92.65   $92.70  
  Purchase #3 $25.72   5.349%   $27.0958   $27.10   $27.10   $27.10  
  Purchase #4 $111.88   4.785%   $117.2335   $117.23   $117.25   $117.20  
  Purchase #5 $97.42   4.734%   $102.0319   $102.03   $102.05   $102.00  
  Purchase #6 $230.94   12.596%   $260.0292   $260.03   $260.05   $260.00  
  Purchase #7 $232.41   11.412%   $258.9326   $258.93   $258.95   $258.90  
  7 purchase totals = $1,016.31       $1,125.6328   $1,125.63   $1,125.70   $1,125.60