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 $86.50   13.486%   $98.1654   $98.17   $98.15   $98.20  
  Purchase #2 $135.41   13.461%   $153.6375   $153.64   $153.65   $153.60  
  Purchase #3 $239.27   4.556%   $250.1711   $250.17   $250.15   $250.20  
  Purchase #4 $51.25   5.446%   $54.0411   $54.04   $54.05   $54.00  
  Purchase #5 $190.34   6.494%   $202.7007   $202.70   $202.70   $202.70  
  Purchase #6 $153.94   3.202%   $158.8692   $158.87   $158.85   $158.90  
  Purchase #7 $236.73   12.566%   $266.4775   $266.48   $266.50   $266.50  
  7 purchase totals = $1,093.44       $1,184.0625   $1,184.07   $1,184.05   $1,184.10