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 $71.35   3.787%   $74.052   $74.05   $74.05   $74.10  
  Purchase #2 $87.61   4.444%   $91.5034   $91.50   $91.50   $91.50  
  Purchase #3 $14.48   12.358%   $16.2694   $16.27   $16.25   $16.30  
  Purchase #4 $95.93   9.725%   $105.2592   $105.26   $105.25   $105.30  
  Purchase #5 $249.32   11.691%   $278.468   $278.47   $278.45   $278.50  
  Purchase #6 $184.82   12.827%   $208.5269   $208.53   $208.55   $208.50  
  Purchase #7 $52.64   11.725%   $58.812   $58.81   $58.80   $58.80  
  7 purchase totals = $756.15       $832.8909   $832.89   $832.85   $833.00