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 $114.48   8.266%   $123.9429   $123.94   $123.95   $123.90  
  Purchase #2 $250.42   7.429%   $269.0237   $269.02   $269.00   $269.00  
  Purchase #3 $179.34   9.142%   $195.7353   $195.74   $195.75   $195.70  
  Purchase #4 $49.53   8.561%   $53.7703   $53.77   $53.75   $53.80  
  Purchase #5 $109.66   4.512%   $114.6079   $114.61   $114.60   $114.60  
  Purchase #6 $242.39   6.267%   $257.5806   $257.58   $257.60   $257.60  
  Purchase #7 $184.92   5.135%   $194.4156   $194.42   $194.40   $194.40  
  7 purchase totals = $1,130.74       $1,209.0763   $1,209.08   $1,209.05   $1,209.00