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 $56.59   11.393%   $63.0373   $63.04   $63.05   $63.00  
  Purchase #2 $172.46   7.328%   $185.0979   $185.10   $185.10   $185.10  
  Purchase #3 $119.59   13.859%   $136.164   $136.16   $136.15   $136.20  
  Purchase #4 $92.42   7.382%   $99.2424   $99.24   $99.25   $99.20  
  Purchase #5 $234.73   6.854%   $250.8184   $250.82   $250.80   $250.80  
  Purchase #6 $143.94   9.226%   $157.2199   $157.22   $157.20   $157.20  
  Purchase #7 $213.79   12.800%   $241.1551   $241.16   $241.15   $241.20  
  7 purchase totals = $1,033.52       $1,132.7350   $1,132.74   $1,132.70   $1,132.70