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 $62.83   10.606%   $69.4937   $69.49   $69.50   $69.50  
  Purchase #2 $159.54   13.267%   $180.7062   $180.71   $180.70   $180.70  
  Purchase #3 $190.53   5.851%   $201.6779   $201.68   $201.70   $201.70  
  Purchase #4 $69.49   11.464%   $77.4563   $77.46   $77.45   $77.50  
  Purchase #5 $182.82   7.856%   $197.1823   $197.18   $197.20   $197.20  
  Purchase #6 $133.71   5.703%   $141.3355   $141.34   $141.35   $141.30  
  Purchase #7 $187.44   6.785%   $200.1578   $200.16   $200.15   $200.20  
  7 purchase totals = $986.36       $1,068.0097   $1,068.02   $1,068.05   $1,068.10