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 $195.78   5.468%   $206.4853   $206.49   $206.50   $206.50  
  Purchase #2 $107.89   9.399%   $118.0306   $118.03   $118.05   $118.00  
  Purchase #3 $120.34   3.492%   $124.5423   $124.54   $124.55   $124.50  
  Purchase #4 $198.49   7.287%   $212.954   $212.95   $212.95   $213.00  
  Purchase #5 $76.31   6.744%   $81.4563   $81.46   $81.45   $81.50  
  Purchase #6 $240.40   6.120%   $255.1125   $255.11   $255.10   $255.10  
  Purchase #7 $196.58   3.735%   $203.9223   $203.92   $203.90   $203.90  
  7 purchase totals = $1,135.79       $1,202.5033   $1,202.50   $1,202.50   $1,202.50