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 $84.65   12.565%   $95.2863   $95.29   $95.30   $95.30  
  Purchase #2 $144.25   4.544%   $150.8047   $150.80   $150.80   $150.80  
  Purchase #3 $131.84   6.118%   $139.906   $139.91   $139.90   $139.90  
  Purchase #4 $51.94   9.225%   $56.7315   $56.73   $56.75   $56.70  
  Purchase #5 $47.37   8.755%   $51.5172   $51.52   $51.50   $51.50  
  Purchase #6 $78.63   8.608%   $85.3985   $85.40   $85.40   $85.40  
  Purchase #7 $204.91   4.636%   $214.4096   $214.41   $214.40   $214.40  
  7 purchase totals = $743.59       $794.0538   $794.06   $794.05   $794.00