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 $213.54   10.835%   $236.6771   $236.68   $236.70   $236.70  
  Purchase #2 $111.68   12.469%   $125.6054   $125.61   $125.60   $125.60  
  Purchase #3 $14.36   12.318%   $16.1289   $16.13   $16.15   $16.10  
  Purchase #4 $216.77   6.275%   $230.3723   $230.37   $230.35   $230.40  
  Purchase #5 $248.55   5.688%   $262.6875   $262.69   $262.70   $262.70  
  Purchase #6 $117.48   10.141%   $129.3936   $129.39   $129.40   $129.40  
  Purchase #7 $31.68   7.645%   $34.1019   $34.10   $34.10   $34.10  
  7 purchase totals = $954.06       $1,034.9667   $1,034.97   $1,035.00   $1,035.00