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 $195.73   8.262%   $211.9012   $211.90   $211.90   $211.90  
  Purchase #2 $219.92   10.249%   $242.4596   $242.46   $242.45   $242.50  
  Purchase #3 $59.53   13.604%   $67.6285   $67.63   $67.65   $67.60  
  Purchase #4 $202.30   8.608%   $219.714   $219.71   $219.70   $219.70  
  Purchase #5 $114.25   8.870%   $124.384   $124.38   $124.40   $124.40  
  Purchase #6 $21.93   5.314%   $23.0954   $23.10   $23.10   $23.10  
  Purchase #7 $57.97   5.111%   $60.9328   $60.93   $60.95   $60.90  
  7 purchase totals = $871.63       $950.1155   $950.11   $950.15   $950.10