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 $181.49   7.554%   $195.1998   $195.20   $195.20   $195.20  
  Purchase #2 $139.86   13.266%   $158.4138   $158.41   $158.40   $158.40  
  Purchase #3 $218.63   12.375%   $245.6855   $245.69   $245.70   $245.70  
  Purchase #4 $183.77   9.238%   $200.7467   $200.75   $200.75   $200.70  
  Purchase #5 $193.45   6.204%   $205.4516   $205.45   $205.45   $205.50  
  Purchase #6 $33.90   8.624%   $36.8235   $36.82   $36.80   $36.80  
  Purchase #7 $33.70   7.477%   $36.2197   $36.22   $36.20   $36.20  
  7 purchase totals = $984.80       $1,078.5406   $1,078.54   $1,078.50   $1,078.50