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 $41.79   11.864%   $46.748   $46.75   $46.75   $46.70  
  Purchase #2 $119.38   11.271%   $132.8353   $132.84   $132.85   $132.80  
  Purchase #3 $118.55   3.683%   $122.9162   $122.92   $122.90   $122.90  
  Purchase #4 $217.63   8.555%   $236.2482   $236.25   $236.25   $236.20  
  Purchase #5 $63.57   13.271%   $72.0064   $72.01   $72.00   $72.00  
  Purchase #6 $59.32   9.253%   $64.8089   $64.81   $64.80   $64.80  
  Purchase #7 $194.82   5.486%   $205.5078   $205.51   $205.50   $205.50  
  7 purchase totals = $815.06       $881.0708   $881.09   $881.05   $880.90