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 $96.95   6.726%   $103.4709   $103.47   $103.45   $103.50  
  Purchase #2 $214.48   4.665%   $224.4855   $224.49   $224.50   $224.50  
  Purchase #3 $46.25   10.843%   $51.2649   $51.26   $51.25   $51.30  
  Purchase #4 $227.89   8.306%   $246.8185   $246.82   $246.80   $246.80  
  Purchase #5 $218.86   7.179%   $234.572   $234.57   $234.55   $234.60  
  Purchase #6 $211.49   6.423%   $225.074   $225.07   $225.05   $225.10  
  Purchase #7 $10.62   5.370%   $11.1903   $11.19   $11.20   $11.20  
  7 purchase totals = $1,026.54       $1,096.8761   $1,096.87   $1,096.80   $1,097.00