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 $82.26   13.856%   $93.6579   $93.66   $93.65   $93.70  
  Purchase #2 $103.63   10.562%   $114.5754   $114.58   $114.60   $114.60  
  Purchase #3 $55.33   3.376%   $57.1979   $57.20   $57.20   $57.20  
  Purchase #4 $206.27   8.467%   $223.7349   $223.73   $223.75   $223.70  
  Purchase #5 $104.39   6.496%   $111.1712   $111.17   $111.15   $111.20  
  Purchase #6 $52.66   10.782%   $58.3378   $58.34   $58.35   $58.30  
  Purchase #7 $193.97   4.181%   $202.0799   $202.08   $202.10   $202.10  
  7 purchase totals = $798.51       $860.7550   $860.76   $860.80   $860.80