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 $105.49   6.148%   $111.9755   $111.98   $112.00   $112.00  
  Purchase #2 $212.75   10.427%   $234.9334   $234.93   $234.95   $234.90  
  Purchase #3 $45.28   10.732%   $50.1394   $50.14   $50.15   $50.10  
  Purchase #4 $28.93   10.593%   $31.9946   $31.99   $32.00   $32.00  
  Purchase #5 $209.58   8.626%   $227.6584   $227.66   $227.65   $227.70  
  Purchase #6 $195.77   13.788%   $222.7628   $222.76   $222.75   $222.80  
  Purchase #7 $221.28   8.576%   $240.257   $240.26   $240.25   $240.30  
  7 purchase totals = $1,019.08       $1,119.7211   $1,119.72   $1,119.75   $1,119.80