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   5.149%   $125.7477   $125.75   $125.75   $125.70  
  Purchase #2 $232.52   13.462%   $263.8218   $263.82   $263.80   $263.80  
  Purchase #3 $196.71   8.568%   $213.5641   $213.56   $213.55   $213.60  
  Purchase #4 $229.34   8.404%   $248.6137   $248.61   $248.60   $248.60  
  Purchase #5 $89.62   4.353%   $93.5212   $93.52   $93.50   $93.50  
  Purchase #6 $170.53   12.141%   $191.234   $191.23   $191.25   $191.20  
  Purchase #7 $96.32   13.309%   $109.1392   $109.14   $109.15   $109.10  
  7 purchase totals = $1,134.63       $1,245.6417   $1,245.63   $1,245.60   $1,245.50