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 $23.89   6.247%   $25.3824   $25.38   $25.40   $25.40  
  Purchase #2 $88.76   10.658%   $98.22   $98.22   $98.20   $98.20  
  Purchase #3 $29.94   13.349%   $33.9367   $33.94   $33.95   $33.90  
  Purchase #4 $241.99   8.427%   $262.3825   $262.38   $262.40   $262.40  
  Purchase #5 $84.48   5.290%   $88.949   $88.95   $88.95   $88.90  
  Purchase #6 $41.57   5.704%   $43.9412   $43.94   $43.95   $43.90  
  Purchase #7 $183.32   12.455%   $206.1525   $206.15   $206.15   $206.20  
  7 purchase totals = $693.95       $758.9643   $758.96   $759.00   $758.90