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 $82.66   13.319%   $93.6695   $93.67   $93.65   $93.70  
  Purchase #2 $118.50   12.790%   $133.6562   $133.66   $133.65   $133.70  
  Purchase #3 $237.77   11.381%   $264.8306   $264.83   $264.85   $264.80  
  Purchase #4 $210.97   4.340%   $220.1261   $220.13   $220.15   $220.10  
  Purchase #5 $174.63   7.811%   $188.2703   $188.27   $188.25   $188.30  
  Purchase #6 $229.92   12.515%   $258.6945   $258.69   $258.70   $258.70  
  Purchase #7 $69.38   4.791%   $72.704   $72.70   $72.70   $72.70  
  7 purchase totals = $1,123.83       $1,231.9512   $1,231.95   $1,231.95   $1,232.00