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 $63.28   6.745%   $67.5482   $67.55   $67.55   $67.50  
  Purchase #2 $154.48   4.586%   $161.5645   $161.56   $161.55   $161.60  
  Purchase #3 $196.47   5.755%   $207.7768   $207.78   $207.80   $207.80  
  Purchase #4 $143.61   12.410%   $161.432   $161.43   $161.45   $161.40  
  Purchase #5 $52.80   6.543%   $56.2547   $56.25   $56.25   $56.30  
  Purchase #6 $119.69   6.623%   $127.6171   $127.62   $127.60   $127.60  
  Purchase #7 $9.25   13.466%   $10.4956   $10.50   $10.50   $10.50  
  7 purchase totals = $739.58       $792.6889   $792.69   $792.70   $792.70