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 $216.66   10.174%   $238.703   $238.70   $238.70   $238.70  
  Purchase #2 $157.49   5.328%   $165.8811   $165.88   $165.90   $165.90  
  Purchase #3 $157.74   12.123%   $176.8628   $176.86   $176.85   $176.90  
  Purchase #4 $69.60   9.260%   $76.045   $76.05   $76.05   $76.00  
  Purchase #5 $228.48   5.552%   $241.1652   $241.17   $241.15   $241.20  
  Purchase #6 $89.88   4.459%   $93.8877   $93.89   $93.90   $93.90  
  Purchase #7 $103.67   9.547%   $113.5674   $113.57   $113.55   $113.60  
  7 purchase totals = $1,023.52       $1,106.1122   $1,106.12   $1,106.10   $1,106.20