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 $58.57   5.223%   $61.6291   $61.63   $61.65   $61.60  
  Purchase #2 $98.38   6.479%   $104.754   $104.75   $104.75   $104.80  
  Purchase #3 $73.71   3.300%   $76.1424   $76.14   $76.15   $76.10  
  Purchase #4 $217.70   4.537%   $227.577   $227.58   $227.60   $227.60  
  Purchase #5 $5.55   5.520%   $5.8564   $5.86   $5.85   $5.90  
  Purchase #6 $131.42   7.390%   $141.1319   $141.13   $141.15   $141.10  
  Purchase #7 $131.69   3.873%   $136.7904   $136.79   $136.80   $136.80  
  7 purchase totals = $717.02       $753.8812   $753.88   $753.95   $753.90