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 $163.31   11.859%   $182.6769   $182.68   $182.70   $182.70  
  Purchase #2 $194.88   10.721%   $215.7731   $215.77   $215.75   $215.80  
  Purchase #3 $9.64   11.865%   $10.7838   $10.78   $10.80   $10.80  
  Purchase #4 $225.44   4.485%   $235.551   $235.55   $235.55   $235.60  
  Purchase #5 $235.60   7.402%   $253.0391   $253.04   $253.05   $253.00  
  Purchase #6 $208.59   5.599%   $220.269   $220.27   $220.25   $220.30  
  Purchase #7 $127.71   7.676%   $137.513   $137.51   $137.50   $137.50  
  7 purchase totals = $1,165.17       $1,255.6059   $1,255.60   $1,255.60   $1,255.70