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 $110.53   13.490%   $125.4405   $125.44   $125.45   $125.40  
  Purchase #2 $203.82   10.426%   $225.0703   $225.07   $225.05   $225.10  
  Purchase #3 $246.32   10.167%   $271.3634   $271.36   $271.35   $271.40  
  Purchase #4 $207.45   5.536%   $218.9344   $218.93   $218.95   $218.90  
  Purchase #5 $30.80   12.266%   $34.5779   $34.58   $34.60   $34.60  
  Purchase #6 $151.78   7.558%   $163.2515   $163.25   $163.25   $163.30  
  Purchase #7 $160.98   3.217%   $166.1587   $166.16   $166.15   $166.20  
  7 purchase totals = $1,111.68       $1,204.7967   $1,204.79   $1,204.80   $1,204.90