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 $54.86   12.697%   $61.8256   $61.83   $61.85   $61.80  
  Purchase #2 $179.26   3.283%   $185.1451   $185.15   $185.15   $185.10  
  Purchase #3 $198.77   3.598%   $205.9217   $205.92   $205.90   $205.90  
  Purchase #4 $243.26   7.613%   $261.7794   $261.78   $261.80   $261.80  
  Purchase #5 $243.28   13.348%   $275.753   $275.75   $275.75   $275.80  
  Purchase #6 $184.77   5.744%   $195.3832   $195.38   $195.40   $195.40  
  Purchase #7 $68.48   11.134%   $76.1046   $76.10   $76.10   $76.10  
  7 purchase totals = $1,172.68       $1,261.9126   $1,261.91   $1,261.95   $1,261.90