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 $84.76   13.248%   $95.989   $95.99   $96.00   $96.00  
  Purchase #2 $226.48   7.158%   $242.6914   $242.69   $242.70   $242.70  
  Purchase #3 $69.46   13.244%   $78.6593   $78.66   $78.65   $78.70  
  Purchase #4 $95.66   4.855%   $100.3043   $100.30   $100.30   $100.30  
  Purchase #5 $204.50   10.173%   $225.3038   $225.30   $225.30   $225.30  
  Purchase #6 $96.80   12.672%   $109.0665   $109.07   $109.05   $109.10  
  Purchase #7 $119.53   8.657%   $129.8777   $129.88   $129.90   $129.90  
  7 purchase totals = $897.19       $981.8920   $981.89   $981.90   $982.00