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 $243.66   9.679%   $267.2439   $267.24   $267.25   $267.20  
  Purchase #2 $119.30   4.108%   $124.2008   $124.20   $124.20   $124.20  
  Purchase #3 $69.74   6.334%   $74.1573   $74.16   $74.15   $74.20  
  Purchase #4 $153.48   7.253%   $164.6119   $164.61   $164.60   $164.60  
  Purchase #5 $213.84   11.194%   $237.7772   $237.78   $237.80   $237.80  
  Purchase #6 $188.97   7.299%   $202.7629   $202.76   $202.75   $202.80  
  Purchase #7 $182.69   3.751%   $189.5427   $189.54   $189.55   $189.50  
  7 purchase totals = $1,171.68       $1,260.2967   $1,260.29   $1,260.30   $1,260.30