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 $87.85   11.255%   $97.7375   $97.74   $97.75   $97.70  
  Purchase #2 $210.27   11.713%   $234.8989   $234.90   $234.90   $234.90  
  Purchase #3 $159.86   9.423%   $174.9236   $174.92   $174.90   $174.90  
  Purchase #4 $222.95   5.288%   $234.7396   $234.74   $234.75   $234.70  
  Purchase #5 $12.76   12.852%   $14.3999   $14.40   $14.40   $14.40  
  Purchase #6 $114.27   4.116%   $118.9734   $118.97   $118.95   $119.00  
  Purchase #7 $248.27   12.153%   $278.4423   $278.44   $278.45   $278.40  
  7 purchase totals = $1,056.23       $1,154.1152   $1,154.11   $1,154.10   $1,154.00