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 $102.83   11.113%   $114.2575   $114.26   $114.25   $114.30  
  Purchase #2 $77.36   12.269%   $86.8513   $86.85   $86.85   $86.90  
  Purchase #3 $86.28   12.690%   $97.2289   $97.23   $97.25   $97.20  
  Purchase #4 $198.93   5.617%   $210.1039   $210.10   $210.10   $210.10  
  Purchase #5 $204.42   13.444%   $231.9022   $231.90   $231.90   $231.90  
  Purchase #6 $158.49   6.111%   $168.1753   $168.18   $168.20   $168.20  
  Purchase #7 $181.95   8.255%   $196.97   $196.97   $196.95   $197.00  
  7 purchase totals = $1,010.26       $1,105.4891   $1,105.49   $1,105.50   $1,105.60