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 $239.41   9.462%   $262.063   $262.06   $262.05   $262.10  
  Purchase #2 $208.95   3.557%   $216.3824   $216.38   $216.40   $216.40  
  Purchase #3 $109.90   7.298%   $117.9205   $117.92   $117.90   $117.90  
  Purchase #4 $122.39   9.465%   $133.9742   $133.97   $133.95   $134.00  
  Purchase #5 $116.79   6.721%   $124.6395   $124.64   $124.65   $124.60  
  Purchase #6 $81.87   13.501%   $92.9233   $92.92   $92.90   $92.90  
  Purchase #7 $223.95   9.755%   $245.7963   $245.80   $245.80   $245.80  
  7 purchase totals = $1,103.26       $1,193.6992   $1,193.69   $1,193.65   $1,193.70