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 $56.85   10.731%   $62.9506   $62.95   $62.95   $63.00  
  Purchase #2 $106.48   10.130%   $117.2664   $117.27   $117.25   $117.30  
  Purchase #3 $182.78   13.819%   $208.0384   $208.04   $208.05   $208.00  
  Purchase #4 $203.39   6.227%   $216.0551   $216.06   $216.05   $216.10  
  Purchase #5 $107.37   6.610%   $114.4672   $114.47   $114.45   $114.50  
  Purchase #6 $12.48   13.757%   $14.1969   $14.20   $14.20   $14.20  
  Purchase #7 $22.32   8.847%   $24.2947   $24.29   $24.30   $24.30  
  7 purchase totals = $691.67       $757.2693   $757.28   $757.25   $757.40