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 $67.62   13.153%   $76.5141   $76.51   $76.50   $76.50  
  Purchase #2 $214.27   11.776%   $239.5024   $239.50   $239.50   $239.50  
  Purchase #3 $218.99   6.216%   $232.6024   $232.60   $232.60   $232.60  
  Purchase #4 $206.93   11.469%   $230.6628   $230.66   $230.65   $230.70  
  Purchase #5 $177.90   4.371%   $185.676   $185.68   $185.70   $185.70  
  Purchase #6 $36.25   13.292%   $41.0684   $41.07   $41.05   $41.10  
  Purchase #7 $85.56   11.679%   $95.5526   $95.55   $95.55   $95.60  
  7 purchase totals = $1,007.52       $1,101.5787   $1,101.57   $1,101.55   $1,101.70