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 $162.27   8.808%   $176.5627   $176.56   $176.55   $176.60  
  Purchase #2 $237.75   12.365%   $267.1478   $267.15   $267.15   $267.10  
  Purchase #3 $51.48   9.265%   $56.2496   $56.25   $56.25   $56.20  
  Purchase #4 $16.60   5.816%   $17.5655   $17.57   $17.55   $17.60  
  Purchase #5 $19.75   12.835%   $22.2849   $22.28   $22.30   $22.30  
  Purchase #6 $173.65   5.167%   $182.6225   $182.62   $182.60   $182.60  
  Purchase #7 $220.25   7.577%   $236.9383   $236.94   $236.95   $236.90  
  7 purchase totals = $881.75       $959.3713   $959.37   $959.35   $959.30