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 $164.32   11.126%   $182.6022   $182.60   $182.60   $182.60  
  Purchase #2 $47.93   11.573%   $53.4769   $53.48   $53.50   $53.50  
  Purchase #3 $125.86   10.165%   $138.6537   $138.65   $138.65   $138.70  
  Purchase #4 $98.61   13.679%   $112.0989   $112.10   $112.10   $112.10  
  Purchase #5 $161.77   8.677%   $175.8068   $175.81   $175.80   $175.80  
  Purchase #6 $149.80   9.490%   $164.016   $164.02   $164.00   $164.00  
  Purchase #7 $169.63   8.330%   $183.7602   $183.76   $183.75   $183.80  
  7 purchase totals = $917.92       $1,010.4147   $1,010.42   $1,010.40   $1,010.50