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 $154.26   5.473%   $162.7026   $162.70   $162.70   $162.70  
  Purchase #2 $23.80   10.474%   $26.2928   $26.29   $26.30   $26.30  
  Purchase #3 $121.67   6.724%   $129.8511   $129.85   $129.85   $129.90  
  Purchase #4 $242.49   13.229%   $274.569   $274.57   $274.55   $274.60  
  Purchase #5 $217.55   9.229%   $237.6277   $237.63   $237.65   $237.60  
  Purchase #6 $21.38   12.590%   $24.0717   $24.07   $24.05   $24.10  
  Purchase #7 $161.35   5.225%   $169.7805   $169.78   $169.80   $169.80  
  7 purchase totals = $942.50       $1,024.8954   $1,024.89   $1,024.90   $1,025.00