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 $118.98   5.295%   $125.28   $125.28   $125.30   $125.30  
  Purchase #2 $186.66   10.304%   $205.8934   $205.89   $205.90   $205.90  
  Purchase #3 $66.30   3.870%   $68.8658   $68.87   $68.85   $68.90  
  Purchase #4 $25.43   8.719%   $27.6472   $27.65   $27.65   $27.60  
  Purchase #5 $208.52   13.734%   $237.1581   $237.16   $237.15   $237.20  
  Purchase #6 $157.80   12.511%   $177.5424   $177.54   $177.55   $177.50  
  Purchase #7 $124.63   13.473%   $141.4214   $141.42   $141.40   $141.40  
  7 purchase totals = $888.32       $983.8083   $983.81   $983.80   $983.80