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 $90.97   5.179%   $95.6813   $95.68   $95.70   $95.70  
  Purchase #2 $72.79   5.710%   $76.9463   $76.95   $76.95   $76.90  
  Purchase #3 $86.70   12.194%   $97.2722   $97.27   $97.25   $97.30  
  Purchase #4 $195.39   5.155%   $205.4624   $205.46   $205.45   $205.50  
  Purchase #5 $68.94   3.297%   $71.213   $71.21   $71.20   $71.20  
  Purchase #6 $208.59   8.299%   $225.9009   $225.90   $225.90   $225.90  
  Purchase #7 $236.28   12.172%   $265.04   $265.04   $265.05   $265.00  
  7 purchase totals = $959.66       $1,037.5161   $1,037.51   $1,037.50   $1,037.50