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 $59.70   8.804%   $64.956   $64.96   $64.95   $65.00  
  Purchase #2 $89.56   5.166%   $94.1867   $94.19   $94.20   $94.20  
  Purchase #3 $64.28   7.546%   $69.1306   $69.13   $69.15   $69.10  
  Purchase #4 $127.41   13.526%   $144.6435   $144.64   $144.65   $144.60  
  Purchase #5 $16.50   13.536%   $18.7334   $18.73   $18.75   $18.70  
  Purchase #6 $114.61   9.713%   $125.7421   $125.74   $125.75   $125.70  
  Purchase #7 $239.56   12.648%   $269.8595   $269.86   $269.85   $269.90  
  7 purchase totals = $711.62       $787.2518   $787.25   $787.30   $787.20