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 $174.47   11.373%   $194.3125   $194.31   $194.30   $194.30  
  Purchase #2 $226.33   4.581%   $236.6982   $236.70   $236.70   $236.70  
  Purchase #3 $219.66   4.189%   $228.8616   $228.86   $228.85   $228.90  
  Purchase #4 $26.65   10.468%   $29.4397   $29.44   $29.45   $29.40  
  Purchase #5 $69.94   7.783%   $75.3834   $75.38   $75.40   $75.40  
  Purchase #6 $241.43   3.398%   $249.6338   $249.63   $249.65   $249.60  
  Purchase #7 $83.46   8.322%   $90.4055   $90.41   $90.40   $90.40  
  7 purchase totals = $1,041.94       $1,104.7347   $1,104.73   $1,104.75   $1,104.70