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 $235.57   13.661%   $267.7512   $267.75   $267.75   $267.80  
  Purchase #2 $204.91   12.362%   $230.241   $230.24   $230.25   $230.20  
  Purchase #3 $164.75   7.859%   $177.6977   $177.70   $177.70   $177.70  
  Purchase #4 $227.69   9.368%   $249.02   $249.02   $249.00   $249.00  
  Purchase #5 $193.50   5.682%   $204.4947   $204.49   $204.50   $204.50  
  Purchase #6 $145.46   12.766%   $164.0294   $164.03   $164.05   $164.00  
  Purchase #7 $175.76   6.853%   $187.8048   $187.80   $187.80   $187.80  
  7 purchase totals = $1,347.64       $1,481.0388   $1,481.03   $1,481.05   $1,481.00