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 $193.73   7.748%   $208.7402   $208.74   $208.75   $208.70  
  Purchase #2 $160.92   6.813%   $171.8835   $171.88   $171.90   $171.90  
  Purchase #3 $188.59   5.825%   $199.5754   $199.58   $199.60   $199.60  
  Purchase #4 $72.91   5.455%   $76.8872   $76.89   $76.90   $76.90  
  Purchase #5 $51.30   5.357%   $54.0481   $54.05   $54.05   $54.00  
  Purchase #6 $183.74   12.477%   $206.6652   $206.67   $206.65   $206.70  
  Purchase #7 $186.87   4.575%   $195.4193   $195.42   $195.40   $195.40  
  7 purchase totals = $1,038.06       $1,113.2189   $1,113.23   $1,113.25   $1,113.20