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 $43.82   9.600%   $48.0267   $48.03   $48.05   $48.00  
  Purchase #2 $248.43   5.176%   $261.2887   $261.29   $261.30   $261.30  
  Purchase #3 $32.89   5.697%   $34.7637   $34.76   $34.75   $34.80  
  Purchase #4 $99.51   8.297%   $107.7663   $107.77   $107.75   $107.80  
  Purchase #5 $123.41   8.319%   $133.6765   $133.68   $133.70   $133.70  
  Purchase #6 $246.92   5.188%   $259.7302   $259.73   $259.75   $259.70  
  Purchase #7 $98.52   12.256%   $110.5946   $110.59   $110.60   $110.60  
  7 purchase totals = $893.50       $955.8467   $955.85   $955.90   $955.90