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 $75.31   9.183%   $82.2257   $82.23   $82.25   $82.20  
  Purchase #2 $135.62   9.626%   $148.6748   $148.67   $148.65   $148.70  
  Purchase #3 $191.60   9.195%   $209.2176   $209.22   $209.20   $209.20  
  Purchase #4 $125.95   8.377%   $136.5008   $136.50   $136.50   $136.50  
  Purchase #5 $179.36   5.433%   $189.1046   $189.10   $189.10   $189.10  
  Purchase #6 $40.54   4.686%   $42.4397   $42.44   $42.45   $42.40  
  Purchase #7 $197.56   8.314%   $213.9851   $213.99   $214.00   $214.00  
  7 purchase totals = $945.94       $1,022.1483   $1,022.15   $1,022.15   $1,022.10