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 $105.81   12.461%   $118.995   $119.00   $119.00   $119.00  
  Purchase #2 $146.69   12.798%   $165.4634   $165.46   $165.45   $165.50  
  Purchase #3 $23.65   10.486%   $26.1299   $26.13   $26.15   $26.10  
  Purchase #4 $137.65   11.497%   $153.4756   $153.48   $153.50   $153.50  
  Purchase #5 $214.66   11.640%   $239.6464   $239.65   $239.65   $239.60  
  Purchase #6 $32.59   7.414%   $35.0062   $35.01   $35.00   $35.00  
  Purchase #7 $203.94   11.214%   $226.8098   $226.81   $226.80   $226.80  
  7 purchase totals = $864.99       $965.5263   $965.54   $965.55   $965.50