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 $107.33   11.614%   $119.7953   $119.80   $119.80   $119.80  
  Purchase #2 $124.97   4.690%   $130.8311   $130.83   $130.85   $130.80  
  Purchase #3 $90.90   8.462%   $98.592   $98.59   $98.60   $98.60  
  Purchase #4 $161.89   7.662%   $174.294   $174.29   $174.30   $174.30  
  Purchase #5 $242.60   9.280%   $265.1133   $265.11   $265.10   $265.10  
  Purchase #6 $89.86   6.772%   $95.9453   $95.95   $95.95   $95.90  
  Purchase #7 $235.62   5.837%   $249.3731   $249.37   $249.35   $249.40  
  7 purchase totals = $1,053.17       $1,133.9441   $1,133.94   $1,133.95   $1,133.90