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 $69.53   8.767%   $75.6257   $75.63   $75.65   $75.60  
  Purchase #2 $196.47   4.516%   $205.3426   $205.34   $205.35   $205.30  
  Purchase #3 $218.89   13.451%   $248.3329   $248.33   $248.35   $248.30  
  Purchase #4 $240.83   12.566%   $271.0927   $271.09   $271.10   $271.10  
  Purchase #5 $40.86   9.311%   $44.6645   $44.66   $44.65   $44.70  
  Purchase #6 $73.51   4.628%   $76.912   $76.91   $76.90   $76.90  
  Purchase #7 $126.83   12.319%   $142.4542   $142.45   $142.45   $142.50  
  7 purchase totals = $966.92       $1,064.4246   $1,064.41   $1,064.45   $1,064.40