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 $55.81   9.740%   $61.2459   $61.25   $61.25   $61.20  
  Purchase #2 $250.57   6.806%   $267.6238   $267.62   $267.60   $267.60  
  Purchase #3 $112.94   5.120%   $118.7225   $118.72   $118.70   $118.70  
  Purchase #4 $221.97   6.345%   $236.054   $236.05   $236.05   $236.10  
  Purchase #5 $140.32   10.395%   $154.9063   $154.91   $154.90   $154.90  
  Purchase #6 $161.38   9.476%   $176.6724   $176.67   $176.65   $176.70  
  Purchase #7 $131.40   4.776%   $137.6757   $137.68   $137.70   $137.70  
  7 purchase totals = $1,074.39       $1,152.9006   $1,152.90   $1,152.85   $1,152.90