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 $126.47   5.323%   $133.202   $133.20   $133.20   $133.20  
  Purchase #2 $162.79   3.843%   $169.046   $169.05   $169.05   $169.00  
  Purchase #3 $30.65   8.217%   $33.1685   $33.17   $33.15   $33.20  
  Purchase #4 $81.41   3.580%   $84.3245   $84.32   $84.30   $84.30  
  Purchase #5 $69.94   12.525%   $78.7   $78.70   $78.70   $78.70  
  Purchase #6 $196.40   3.865%   $203.9909   $203.99   $204.00   $204.00  
  Purchase #7 $223.71   7.569%   $240.6426   $240.64   $240.65   $240.60  
  7 purchase totals = $891.37       $943.0745   $943.07   $943.05   $943.00