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 $196.28   5.448%   $206.9733   $206.97   $206.95   $207.00  
  Purchase #2 $102.66   11.829%   $114.8037   $114.80   $114.80   $114.80  
  Purchase #3 $67.44   8.792%   $73.3693   $73.37   $73.35   $73.40  
  Purchase #4 $9.71   5.803%   $10.2735   $10.27   $10.25   $10.30  
  Purchase #5 $200.54   5.570%   $211.7101   $211.71   $211.70   $211.70  
  Purchase #6 $83.87   11.388%   $93.4211   $93.42   $93.40   $93.40  
  Purchase #7 $78.56   5.528%   $82.9028   $82.90   $82.90   $82.90  
  7 purchase totals = $739.06       $793.4538   $793.44   $793.35   $793.50