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 $212.99   7.813%   $229.6309   $229.63   $229.65   $229.60  
  Purchase #2 $178.85   6.600%   $190.6541   $190.65   $190.65   $190.70  
  Purchase #3 $68.37   5.853%   $72.3717   $72.37   $72.35   $72.40  
  Purchase #4 $207.69   13.697%   $236.1373   $236.14   $236.15   $236.10  
  Purchase #5 $168.89   13.209%   $191.1987   $191.20   $191.20   $191.20  
  Purchase #6 $57.92   3.502%   $59.9484   $59.95   $59.95   $59.90  
  Purchase #7 $49.58   5.218%   $52.1671   $52.17   $52.15   $52.20  
  7 purchase totals = $944.29       $1,032.1082   $1,032.11   $1,032.10   $1,032.10