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 $112.95   11.582%   $126.0319   $126.03   $126.05   $126.00  
  Purchase #2 $240.56   5.124%   $252.8863   $252.89   $252.90   $252.90  
  Purchase #3 $108.72   8.254%   $117.6937   $117.69   $117.70   $117.70  
  Purchase #4 $206.88   9.835%   $227.2266   $227.23   $227.25   $227.20  
  Purchase #5 $224.67   8.464%   $243.6861   $243.69   $243.70   $243.70  
  Purchase #6 $222.73   6.197%   $236.5326   $236.53   $236.55   $236.50  
  Purchase #7 $10.54   11.654%   $11.7683   $11.77   $11.75   $11.80  
  7 purchase totals = $1,127.05       $1,215.8255   $1,215.83   $1,215.90   $1,215.80