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 $119.72   6.858%   $127.9304   $127.93   $127.95   $127.90  
  Purchase #2 $132.84   12.124%   $148.9455   $148.95   $148.95   $148.90  
  Purchase #3 $74.25   12.664%   $83.653   $83.65   $83.65   $83.70  
  Purchase #4 $204.50   5.845%   $216.453   $216.45   $216.45   $216.50  
  Purchase #5 $247.79   5.539%   $261.5151   $261.52   $261.50   $261.50  
  Purchase #6 $143.74   12.708%   $162.0065   $162.01   $162.00   $162.00  
  Purchase #7 $137.70   11.852%   $154.0202   $154.02   $154.00   $154.00  
  7 purchase totals = $1,060.54       $1,154.5237   $1,154.53   $1,154.50   $1,154.50