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 $69.91   8.871%   $76.1117   $76.11   $76.10   $76.10  
  Purchase #2 $248.54   5.143%   $261.3224   $261.32   $261.30   $261.30  
  Purchase #3 $50.60   9.855%   $55.5866   $55.59   $55.60   $55.60  
  Purchase #4 $167.52   5.594%   $176.8911   $176.89   $176.90   $176.90  
  Purchase #5 $96.34   6.787%   $102.8786   $102.88   $102.90   $102.90  
  Purchase #6 $101.57   12.824%   $114.5953   $114.60   $114.60   $114.60  
  Purchase #7 $206.60   6.361%   $219.7418   $219.74   $219.75   $219.70  
  7 purchase totals = $941.08       $1,007.1275   $1,007.13   $1,007.15   $1,007.10