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 $86.27   10.731%   $95.5276   $95.53   $95.55   $95.50  
  Purchase #2 $101.27   3.567%   $104.8823   $104.88   $104.90   $104.90  
  Purchase #3 $155.90   3.529%   $161.4017   $161.40   $161.40   $161.40  
  Purchase #4 $24.46   7.846%   $26.3791   $26.38   $26.40   $26.40  
  Purchase #5 $177.74   3.403%   $183.7885   $183.79   $183.80   $183.80  
  Purchase #6 $100.45   3.696%   $104.1626   $104.16   $104.15   $104.20  
  Purchase #7 $188.54   12.731%   $212.543   $212.54   $212.55   $212.50  
  7 purchase totals = $834.63       $888.6848   $888.68   $888.75   $888.70