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 $68.35   12.273%   $76.7386   $76.74   $76.75   $76.70  
  Purchase #2 $137.62   3.788%   $142.833   $142.83   $142.85   $142.80  
  Purchase #3 $96.99   13.214%   $109.8063   $109.81   $109.80   $109.80  
  Purchase #4 $222.61   12.244%   $249.8664   $249.87   $249.85   $249.90  
  Purchase #5 $183.95   8.773%   $200.0879   $200.09   $200.10   $200.10  
  Purchase #6 $105.27   6.425%   $112.0336   $112.03   $112.05   $112.00  
  Purchase #7 $217.30   10.784%   $240.7336   $240.73   $240.75   $240.70  
  7 purchase totals = $1,032.09       $1,132.0994   $1,132.10   $1,132.15   $1,132.00