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 $68.87   4.471%   $71.9492   $71.95   $71.95   $71.90  
  Purchase #2 $58.26   8.483%   $63.2022   $63.20   $63.20   $63.20  
  Purchase #3 $25.82   8.185%   $27.9334   $27.93   $27.95   $27.90  
  Purchase #4 $209.91   8.355%   $227.448   $227.45   $227.45   $227.40  
  Purchase #5 $161.32   7.356%   $173.1867   $173.19   $173.20   $173.20  
  Purchase #6 $123.72   11.833%   $138.3598   $138.36   $138.35   $138.40  
  Purchase #7 $183.73   7.168%   $196.8998   $196.90   $196.90   $196.90  
  7 purchase totals = $831.63       $898.9791   $898.98   $899.00   $898.90