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 $119.59   4.527%   $125.0038   $125.00   $125.00   $125.00  
  Purchase #2 $211.36   9.183%   $230.7692   $230.77   $230.75   $230.80  
  Purchase #3 $192.94   7.510%   $207.4298   $207.43   $207.45   $207.40  
  Purchase #4 $41.54   5.807%   $43.9522   $43.95   $43.95   $44.00  
  Purchase #5 $209.71   10.257%   $231.22   $231.22   $231.20   $231.20  
  Purchase #6 $54.93   13.630%   $62.417   $62.42   $62.40   $62.40  
  Purchase #7 $39.83   7.214%   $42.7033   $42.70   $42.70   $42.70  
  7 purchase totals = $869.90       $943.4953   $943.49   $943.45   $943.50