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 $240.79   8.742%   $261.8399   $261.84   $261.85   $261.80  
  Purchase #2 $58.43   9.281%   $63.8529   $63.85   $63.85   $63.90  
  Purchase #3 $174.86   12.771%   $197.1914   $197.19   $197.20   $197.20  
  Purchase #4 $58.71   5.639%   $62.0207   $62.02   $62.00   $62.00  
  Purchase #5 $224.54   10.573%   $248.2806   $248.28   $248.30   $248.30  
  Purchase #6 $99.30   8.458%   $107.6988   $107.70   $107.70   $107.70  
  Purchase #7 $174.93   3.628%   $181.2765   $181.28   $181.30   $181.30  
  7 purchase totals = $1,031.56       $1,122.1608   $1,122.16   $1,122.20   $1,122.20