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 $205.46   4.132%   $213.9496   $213.95   $213.95   $213.90  
  Purchase #2 $210.86   13.164%   $238.6176   $238.62   $238.60   $238.60  
  Purchase #3 $28.99   13.656%   $32.9489   $32.95   $32.95   $32.90  
  Purchase #4 $117.86   3.427%   $121.8991   $121.90   $121.90   $121.90  
  Purchase #5 $98.67   6.343%   $104.9286   $104.93   $104.95   $104.90  
  Purchase #6 $44.25   7.466%   $47.5537   $47.55   $47.55   $47.60  
  Purchase #7 $231.27   8.509%   $250.9488   $250.95   $250.95   $250.90  
  7 purchase totals = $937.36       $1,010.8463   $1,010.85   $1,010.85   $1,010.70