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 $92.70   3.544%   $95.9853   $95.99   $96.00   $96.00  
  Purchase #2 $132.81   5.356%   $139.9233   $139.92   $139.90   $139.90  
  Purchase #3 $164.83   3.736%   $170.988   $170.99   $171.00   $171.00  
  Purchase #4 $179.53   3.544%   $185.8925   $185.89   $185.90   $185.90  
  Purchase #5 $217.67   12.445%   $244.759   $244.76   $244.75   $244.80  
  Purchase #6 $125.74   5.500%   $132.6557   $132.66   $132.65   $132.70  
  Purchase #7 $172.48   9.239%   $188.4154   $188.42   $188.40   $188.40  
  7 purchase totals = $1,085.76       $1,158.6192   $1,158.63   $1,158.60   $1,158.70