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 $196.49   5.331%   $206.9649   $206.96   $206.95   $207.00  
  Purchase #2 $182.55   8.848%   $198.702   $198.70   $198.70   $198.70  
  Purchase #3 $166.25   3.360%   $171.836   $171.84   $171.85   $171.80  
  Purchase #4 $113.34   6.537%   $120.749   $120.75   $120.75   $120.70  
  Purchase #5 $143.73   7.841%   $154.9999   $155.00   $155.00   $155.00  
  Purchase #6 $120.70   7.857%   $130.1834   $130.18   $130.20   $130.20  
  Purchase #7 $76.75   10.368%   $84.7074   $84.71   $84.70   $84.70  
  7 purchase totals = $999.81       $1,068.1426   $1,068.14   $1,068.15   $1,068.10