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 $69.34   10.549%   $76.6547   $76.65   $76.65   $76.70  
  Purchase #2 $45.94   4.859%   $48.1722   $48.17   $48.15   $48.20  
  Purchase #3 $227.33   11.149%   $252.675   $252.68   $252.70   $252.70  
  Purchase #4 $237.91   12.698%   $268.1198   $268.12   $268.10   $268.10  
  Purchase #5 $95.53   8.461%   $103.6128   $103.61   $103.60   $103.60  
  Purchase #6 $158.71   12.574%   $178.6662   $178.67   $178.65   $178.70  
  Purchase #7 $13.62   4.661%   $14.2548   $14.25   $14.25   $14.30  
  7 purchase totals = $848.38       $942.1555   $942.15   $942.10   $942.30