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 $60.53   5.337%   $63.7605   $63.76   $63.75   $63.80  
  Purchase #2 $150.62   11.290%   $167.625   $167.63   $167.65   $167.60  
  Purchase #3 $242.28   4.861%   $254.0572   $254.06   $254.05   $254.10  
  Purchase #4 $194.55   10.292%   $214.5731   $214.57   $214.55   $214.60  
  Purchase #5 $50.50   12.773%   $56.9504   $56.95   $56.95   $57.00  
  Purchase #6 $242.77   8.213%   $262.7087   $262.71   $262.70   $262.70  
  Purchase #7 $188.97   12.358%   $212.3229   $212.32   $212.30   $212.30  
  7 purchase totals = $1,130.22       $1,231.9978   $1,232.00   $1,231.95   $1,232.10