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 $32.98   7.491%   $35.4505   $35.45   $35.45   $35.50  
  Purchase #2 $249.75   5.462%   $263.3913   $263.39   $263.40   $263.40  
  Purchase #3 $244.29   7.341%   $262.2233   $262.22   $262.20   $262.20  
  Purchase #4 $90.39   3.472%   $93.5283   $93.53   $93.55   $93.50  
  Purchase #5 $43.90   10.691%   $48.5933   $48.59   $48.60   $48.60  
  Purchase #6 $179.48   10.263%   $197.9   $197.90   $197.90   $197.90  
  Purchase #7 $102.74   10.798%   $113.8339   $113.83   $113.85   $113.80  
  7 purchase totals = $943.53       $1,014.9206   $1,014.91   $1,014.95   $1,014.90