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 $152.57   6.613%   $162.6595   $162.66   $162.65   $162.70  
  Purchase #2 $246.71   8.429%   $267.5052   $267.51   $267.50   $267.50  
  Purchase #3 $43.66   12.573%   $49.1494   $49.15   $49.15   $49.10  
  Purchase #4 $94.96   7.288%   $101.8807   $101.88   $101.90   $101.90  
  Purchase #5 $126.78   12.712%   $142.8963   $142.90   $142.90   $142.90  
  Purchase #6 $159.92   10.810%   $177.2074   $177.21   $177.20   $177.20  
  Purchase #7 $32.94   3.777%   $34.1841   $34.18   $34.20   $34.20  
  7 purchase totals = $857.54       $935.4826   $935.49   $935.50   $935.50