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 $117.83   6.295%   $125.2474   $125.25   $125.25   $125.20  
  Purchase #2 $223.33   9.234%   $243.9523   $243.95   $243.95   $244.00  
  Purchase #3 $10.92   8.257%   $11.8217   $11.82   $11.80   $11.80  
  Purchase #4 $182.66   13.687%   $207.6607   $207.66   $207.65   $207.70  
  Purchase #5 $250.97   7.759%   $270.4428   $270.44   $270.45   $270.40  
  Purchase #6 $230.65   6.528%   $245.7068   $245.71   $245.70   $245.70  
  Purchase #7 $125.41   4.611%   $131.1927   $131.19   $131.20   $131.20  
  7 purchase totals = $1,141.77       $1,236.0244   $1,236.02   $1,236.00   $1,236.00