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 $67.41   10.870%   $74.7375   $74.74   $74.75   $74.70  
  Purchase #2 $240.59   9.710%   $263.9513   $263.95   $263.95   $264.00  
  Purchase #3 $176.74   10.711%   $195.6706   $195.67   $195.65   $195.70  
  Purchase #4 $208.97   4.184%   $217.7133   $217.71   $217.70   $217.70  
  Purchase #5 $58.49   7.252%   $62.7317   $62.73   $62.75   $62.70  
  Purchase #6 $228.65   3.451%   $236.5407   $236.54   $236.55   $236.50  
  Purchase #7 $76.50   8.331%   $82.8732   $82.87   $82.85   $82.90  
  7 purchase totals = $1,057.35       $1,134.2183   $1,134.21   $1,134.20   $1,134.20