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 $182.58   10.457%   $201.6724   $201.67   $201.65   $201.70  
  Purchase #2 $195.83   10.149%   $215.7048   $215.70   $215.70   $215.70  
  Purchase #3 $155.56   11.569%   $173.5567   $173.56   $173.55   $173.60  
  Purchase #4 $131.26   8.357%   $142.2294   $142.23   $142.25   $142.20  
  Purchase #5 $212.54   4.592%   $222.2998   $222.30   $222.30   $222.30  
  Purchase #6 $39.98   4.645%   $41.8371   $41.84   $41.85   $41.80  
  Purchase #7 $37.92   13.232%   $42.9376   $42.94   $42.95   $42.90  
  7 purchase totals = $955.67       $1,040.2378   $1,040.24   $1,040.25   $1,040.20