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 $175.33   11.549%   $195.5789   $195.58   $195.60   $195.60  
  Purchase #2 $118.66   5.592%   $125.2955   $125.30   $125.30   $125.30  
  Purchase #3 $181.44   13.779%   $206.4406   $206.44   $206.45   $206.40  
  Purchase #4 $231.61   11.761%   $258.8497   $258.85   $258.85   $258.80  
  Purchase #5 $247.26   10.762%   $273.8701   $273.87   $273.85   $273.90  
  Purchase #6 $57.42   3.177%   $59.2442   $59.24   $59.25   $59.20  
  Purchase #7 $75.75   10.703%   $83.8575   $83.86   $83.85   $83.90  
  7 purchase totals = $1,087.47       $1,203.1365   $1,203.14   $1,203.15   $1,203.10