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 $225.46   8.347%   $244.2791   $244.28   $244.30   $244.30  
  Purchase #2 $162.25   10.285%   $178.9374   $178.94   $178.95   $178.90  
  Purchase #3 $211.98   4.545%   $221.6145   $221.61   $221.60   $221.60  
  Purchase #4 $213.28   13.554%   $242.188   $242.19   $242.20   $242.20  
  Purchase #5 $118.28   3.516%   $122.4387   $122.44   $122.45   $122.40  
  Purchase #6 $180.80   7.510%   $194.3781   $194.38   $194.40   $194.40  
  Purchase #7 $56.54   8.271%   $61.2164   $61.22   $61.20   $61.20  
  7 purchase totals = $1,168.59       $1,265.0522   $1,265.06   $1,265.10   $1,265.00