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 $64.44   7.489%   $69.2659   $69.27   $69.25   $69.30  
  Purchase #2 $173.46   12.335%   $194.8563   $194.86   $194.85   $194.90  
  Purchase #3 $190.57   12.845%   $215.0487   $215.05   $215.05   $215.00  
  Purchase #4 $112.62   6.327%   $119.7455   $119.75   $119.75   $119.70  
  Purchase #5 $144.61   12.465%   $162.6356   $162.64   $162.65   $162.60  
  Purchase #6 $208.34   13.601%   $236.6763   $236.68   $236.70   $236.70  
  Purchase #7 $170.90   3.417%   $176.7397   $176.74   $176.75   $176.70  
  7 purchase totals = $1,064.94       $1,174.9680   $1,174.99   $1,175.00   $1,174.90