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 $195.62   8.247%   $211.7528   $211.75   $211.75   $211.80  
  Purchase #2 $146.37   8.233%   $158.4206   $158.42   $158.40   $158.40  
  Purchase #3 $133.60   13.208%   $151.2459   $151.25   $151.25   $151.20  
  Purchase #4 $207.79   8.652%   $225.768   $225.77   $225.75   $225.80  
  Purchase #5 $6.44   7.502%   $6.9231   $6.92   $6.90   $6.90  
  Purchase #6 $111.50   11.153%   $123.9356   $123.94   $123.95   $123.90  
  Purchase #7 $196.59   9.495%   $215.2562   $215.26   $215.25   $215.30  
  7 purchase totals = $997.91       $1,093.3022   $1,093.31   $1,093.25   $1,093.30