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 $195.89   3.347%   $202.4464   $202.45   $202.45   $202.40  
  Purchase #2 $76.36   6.860%   $81.5983   $81.60   $81.60   $81.60  
  Purchase #3 $33.38   4.293%   $34.813   $34.81   $34.80   $34.80  
  Purchase #4 $56.49   7.362%   $60.6488   $60.65   $60.65   $60.60  
  Purchase #5 $85.99   10.808%   $95.2838   $95.28   $95.30   $95.30  
  Purchase #6 $92.70   3.672%   $96.1039   $96.10   $96.10   $96.10  
  Purchase #7 $245.58   11.303%   $273.3379   $273.34   $273.35   $273.30  
  7 purchase totals = $786.39       $844.2321   $844.23   $844.25   $844.10