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 $195.84   5.762%   $207.1243   $207.12   $207.10   $207.10  
  Purchase #2 $226.54   13.286%   $256.6381   $256.64   $256.65   $256.60  
  Purchase #3 $183.73   6.552%   $195.768   $195.77   $195.75   $195.80  
  Purchase #4 $67.91   13.305%   $76.9454   $76.95   $76.95   $76.90  
  Purchase #5 $188.47   12.288%   $211.6292   $211.63   $211.65   $211.60  
  Purchase #6 $130.50   9.526%   $142.9314   $142.93   $142.95   $142.90  
  Purchase #7 $74.51   6.821%   $79.5923   $79.59   $79.60   $79.60  
  7 purchase totals = $1,067.50       $1,170.6287   $1,170.63   $1,170.65   $1,170.50