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 $61.56   11.769%   $68.805   $68.81   $68.80   $68.80  
  Purchase #2 $114.99   5.106%   $120.8614   $120.86   $120.85   $120.90  
  Purchase #3 $130.28   6.741%   $139.0622   $139.06   $139.05   $139.10  
  Purchase #4 $239.52   11.551%   $267.187   $267.19   $267.20   $267.20  
  Purchase #5 $160.35   12.669%   $180.6647   $180.66   $180.65   $180.70  
  Purchase #6 $164.58   8.350%   $178.3224   $178.32   $178.30   $178.30  
  Purchase #7 $235.44   6.478%   $250.6918   $250.69   $250.70   $250.70  
  7 purchase totals = $1,106.72       $1,205.5945   $1,205.59   $1,205.55   $1,205.70