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 $57.62   3.215%   $59.4725   $59.47   $59.45   $59.50  
  Purchase #2 $103.41   10.291%   $114.0519   $114.05   $114.05   $114.10  
  Purchase #3 $57.76   8.422%   $62.6245   $62.62   $62.60   $62.60  
  Purchase #4 $178.38   13.262%   $202.0368   $202.04   $202.05   $202.00  
  Purchase #5 $189.48   7.681%   $204.034   $204.03   $204.05   $204.00  
  Purchase #6 $188.73   11.624%   $210.668   $210.67   $210.65   $210.70  
  Purchase #7 $233.33   11.851%   $260.9819   $260.98   $261.00   $261.00  
  7 purchase totals = $1,008.71       $1,113.8696   $1,113.86   $1,113.85   $1,113.90