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 $194.87   5.864%   $206.2972   $206.30   $206.30   $206.30  
  Purchase #2 $179.87   5.796%   $190.2953   $190.30   $190.30   $190.30  
  Purchase #3 $206.74   12.173%   $231.9065   $231.91   $231.90   $231.90  
  Purchase #4 $29.81   11.254%   $33.1648   $33.16   $33.15   $33.20  
  Purchase #5 $125.76   3.490%   $130.149   $130.15   $130.15   $130.10  
  Purchase #6 $106.72   12.114%   $119.6481   $119.65   $119.65   $119.60  
  Purchase #7 $126.63   7.557%   $136.1994   $136.20   $136.20   $136.20  
  7 purchase totals = $970.40       $1,047.6603   $1,047.67   $1,047.65   $1,047.60