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 $247.27   6.742%   $263.9409   $263.94   $263.95   $263.90  
  Purchase #2 $229.88   7.168%   $246.3578   $246.36   $246.35   $246.40  
  Purchase #3 $162.80   7.450%   $174.9286   $174.93   $174.95   $174.90  
  Purchase #4 $208.54   12.243%   $234.0716   $234.07   $234.05   $234.10  
  Purchase #5 $44.83   12.155%   $50.2791   $50.28   $50.30   $50.30  
  Purchase #6 $93.67   8.342%   $101.484   $101.48   $101.50   $101.50  
  Purchase #7 $27.38   10.143%   $30.1572   $30.16   $30.15   $30.20  
  7 purchase totals = $1,014.37       $1,101.2192   $1,101.22   $1,101.25   $1,101.30