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 $55.68   12.459%   $62.6172   $62.62   $62.60   $62.60  
  Purchase #2 $60.95   3.813%   $63.274   $63.27   $63.25   $63.30  
  Purchase #3 $56.40   12.230%   $63.2977   $63.30   $63.30   $63.30  
  Purchase #4 $242.91   9.420%   $265.7921   $265.79   $265.80   $265.80  
  Purchase #5 $195.53   8.601%   $212.3475   $212.35   $212.35   $212.30  
  Purchase #6 $218.84   7.553%   $235.369   $235.37   $235.35   $235.40  
  Purchase #7 $166.81   9.748%   $183.0706   $183.07   $183.05   $183.10  
  7 purchase totals = $997.12       $1,085.7681   $1,085.77   $1,085.70   $1,085.80