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 $222.87   8.236%   $241.2256   $241.23   $241.25   $241.20  
  Purchase #2 $44.30   9.340%   $48.4376   $48.44   $48.45   $48.40  
  Purchase #3 $247.58   9.819%   $271.8899   $271.89   $271.90   $271.90  
  Purchase #4 $248.27   7.230%   $266.2199   $266.22   $266.20   $266.20  
  Purchase #5 $180.84   3.128%   $186.4967   $186.50   $186.50   $186.50  
  Purchase #6 $67.33   5.720%   $71.1813   $71.18   $71.20   $71.20  
  Purchase #7 $114.98   3.725%   $119.263   $119.26   $119.25   $119.30  
  7 purchase totals = $1,126.17       $1,204.7140   $1,204.72   $1,204.75   $1,204.70