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 $85.60   11.214%   $95.1992   $95.20   $95.20   $95.20  
  Purchase #2 $164.41   8.614%   $178.5723   $178.57   $178.55   $178.60  
  Purchase #3 $119.93   5.708%   $126.7756   $126.78   $126.80   $126.80  
  Purchase #4 $146.48   5.664%   $154.7766   $154.78   $154.80   $154.80  
  Purchase #5 $193.99   3.163%   $200.1259   $200.13   $200.15   $200.10  
  Purchase #6 $48.58   12.387%   $54.5976   $54.60   $54.60   $54.60  
  Purchase #7 $140.45   6.631%   $149.7632   $149.76   $149.75   $149.80  
  7 purchase totals = $899.44       $959.8104   $959.82   $959.85   $959.90