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 $69.37   5.587%   $73.2457   $73.25   $73.25   $73.20  
  Purchase #2 $166.39   5.161%   $174.9774   $174.98   $175.00   $175.00  
  Purchase #3 $141.46   10.143%   $155.8083   $155.81   $155.80   $155.80  
  Purchase #4 $241.41   13.462%   $273.9086   $273.91   $273.90   $273.90  
  Purchase #5 $225.44   10.229%   $248.5003   $248.50   $248.50   $248.50  
  Purchase #6 $169.63   13.870%   $193.1577   $193.16   $193.15   $193.20  
  Purchase #7 $243.53   11.867%   $272.4297   $272.43   $272.45   $272.40  
  7 purchase totals = $1,257.23       $1,392.0277   $1,392.04   $1,392.05   $1,392.00