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 $241.89   8.297%   $261.9596   $261.96   $261.95   $262.00  
  Purchase #2 $63.39   4.366%   $66.1576   $66.16   $66.15   $66.20  
  Purchase #3 $108.50   4.772%   $113.6776   $113.68   $113.70   $113.70  
  Purchase #4 $172.51   13.692%   $196.1301   $196.13   $196.15   $196.10  
  Purchase #5 $108.80   9.156%   $118.7617   $118.76   $118.75   $118.80  
  Purchase #6 $22.30   7.106%   $23.8846   $23.88   $23.90   $23.90  
  Purchase #7 $244.30   3.305%   $252.3741   $252.37   $252.35   $252.40  
  7 purchase totals = $961.69       $1,032.9453   $1,032.94   $1,032.95   $1,033.10