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 $71.47   7.252%   $76.653   $76.65   $76.65   $76.70  
  Purchase #2 $214.29   4.380%   $223.6759   $223.68   $223.70   $223.70  
  Purchase #3 $57.38   6.751%   $61.2537   $61.25   $61.25   $61.30  
  Purchase #4 $114.36   6.778%   $122.1113   $122.11   $122.10   $122.10  
  Purchase #5 $168.65   8.407%   $182.8284   $182.83   $182.85   $182.80  
  Purchase #6 $106.54   10.477%   $117.7022   $117.70   $117.70   $117.70  
  Purchase #7 $81.87   13.230%   $92.7014   $92.70   $92.70   $92.70  
  7 purchase totals = $814.56       $876.9259   $876.92   $876.95   $877.00