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 $84.68   9.471%   $92.7   $92.70   $92.70   $92.70  
  Purchase #2 $190.73   8.841%   $207.5924   $207.59   $207.60   $207.60  
  Purchase #3 $207.84   11.219%   $231.1576   $231.16   $231.15   $231.20  
  Purchase #4 $222.30   6.828%   $237.4786   $237.48   $237.50   $237.50  
  Purchase #5 $249.75   4.847%   $261.8554   $261.86   $261.85   $261.90  
  Purchase #6 $141.72   3.319%   $146.4237   $146.42   $146.40   $146.40  
  Purchase #7 $197.84   9.736%   $217.1017   $217.10   $217.10   $217.10  
  7 purchase totals = $1,294.86       $1,394.3094   $1,394.31   $1,394.30   $1,394.40