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 $46.74   12.243%   $52.4624   $52.46   $52.45   $52.50  
  Purchase #2 $145.27   4.774%   $152.2052   $152.21   $152.20   $152.20  
  Purchase #3 $82.43   3.402%   $85.2343   $85.23   $85.25   $85.20  
  Purchase #4 $240.58   4.870%   $252.2962   $252.30   $252.30   $252.30  
  Purchase #5 $218.36   10.633%   $241.5782   $241.58   $241.60   $241.60  
  Purchase #6 $191.33   5.845%   $202.5132   $202.51   $202.50   $202.50  
  Purchase #7 $115.69   3.126%   $119.3065   $119.31   $119.30   $119.30  
  7 purchase totals = $1,040.40       $1,105.5960   $1,105.60   $1,105.60   $1,105.60