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 $211.49   10.508%   $233.7134   $233.71   $233.70   $233.70  
  Purchase #2 $25.97   11.856%   $29.049   $29.05   $29.05   $29.00  
  Purchase #3 $186.61   5.393%   $196.6739   $196.67   $196.65   $196.70  
  Purchase #4 $219.77   7.544%   $236.3494   $236.35   $236.35   $236.30  
  Purchase #5 $43.80   12.228%   $49.1559   $49.16   $49.15   $49.20  
  Purchase #6 $63.82   8.213%   $69.0615   $69.06   $69.05   $69.10  
  Purchase #7 $182.51   9.577%   $199.989   $199.99   $200.00   $200.00  
  7 purchase totals = $933.97       $1,013.9921   $1,013.99   $1,013.95   $1,014.00