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 $196.85   4.160%   $205.039   $205.04   $205.05   $205.00  
  Purchase #2 $117.76   6.474%   $125.3838   $125.38   $125.40   $125.40  
  Purchase #3 $43.66   10.661%   $48.3146   $48.31   $48.30   $48.30  
  Purchase #4 $194.48   7.458%   $208.9843   $208.98   $209.00   $209.00  
  Purchase #5 $109.81   13.143%   $124.2423   $124.24   $124.25   $124.20  
  Purchase #6 $186.71   13.549%   $212.0073   $212.01   $212.00   $212.00  
  Purchase #7 $55.92   8.319%   $60.572   $60.57   $60.55   $60.60  
  7 purchase totals = $905.19       $984.5433   $984.53   $984.55   $984.50