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 $197.77   12.870%   $223.223   $223.22   $223.20   $223.20  
  Purchase #2 $213.89   10.191%   $235.6875   $235.69   $235.70   $235.70  
  Purchase #3 $199.90   3.358%   $206.6126   $206.61   $206.60   $206.60  
  Purchase #4 $169.57   8.462%   $183.919   $183.92   $183.90   $183.90  
  Purchase #5 $180.62   7.714%   $194.553   $194.55   $194.55   $194.60  
  Purchase #6 $124.40   7.418%   $133.628   $133.63   $133.65   $133.60  
  Purchase #7 $26.74   5.359%   $28.173   $28.17   $28.15   $28.20  
  7 purchase totals = $1,112.89       $1,205.7961   $1,205.79   $1,205.75   $1,205.80