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 $57.87   8.287%   $62.6657   $62.67   $62.65   $62.70  
  Purchase #2 $172.28   12.549%   $193.8994   $193.90   $193.90   $193.90  
  Purchase #3 $148.64   7.469%   $159.7419   $159.74   $159.75   $159.70  
  Purchase #4 $246.57   12.425%   $277.2063   $277.21   $277.20   $277.20  
  Purchase #5 $69.86   9.755%   $76.6748   $76.67   $76.65   $76.70  
  Purchase #6 $28.42   4.306%   $29.6438   $29.64   $29.65   $29.60  
  Purchase #7 $73.76   4.615%   $77.164   $77.16   $77.15   $77.20  
  7 purchase totals = $797.40       $876.9959   $876.99   $876.95   $877.00