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 $55.94   10.652%   $61.8987   $61.90   $61.90   $61.90  
  Purchase #2 $225.62   12.843%   $254.5964   $254.60   $254.60   $254.60  
  Purchase #3 $204.85   4.618%   $214.31   $214.31   $214.30   $214.30  
  Purchase #4 $244.28   4.136%   $254.3834   $254.38   $254.40   $254.40  
  Purchase #5 $248.77   5.171%   $261.6339   $261.63   $261.65   $261.60  
  Purchase #6 $98.85   11.719%   $110.4342   $110.43   $110.45   $110.40  
  Purchase #7 $118.91   8.814%   $129.3907   $129.39   $129.40   $129.40  
  7 purchase totals = $1,197.22       $1,286.6473   $1,286.64   $1,286.70   $1,286.60