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 $175.46   11.738%   $196.0555   $196.06   $196.05   $196.10  
  Purchase #2 $201.41   7.575%   $216.6668   $216.67   $216.65   $216.70  
  Purchase #3 $32.58   3.155%   $33.6079   $33.61   $33.60   $33.60  
  Purchase #4 $175.83   6.397%   $187.0778   $187.08   $187.10   $187.10  
  Purchase #5 $236.43   3.266%   $244.1518   $244.15   $244.15   $244.20  
  Purchase #6 $242.43   13.423%   $274.9714   $274.97   $274.95   $275.00  
  Purchase #7 $176.72   7.827%   $190.5519   $190.55   $190.55   $190.60  
  7 purchase totals = $1,240.86       $1,343.0831   $1,343.09   $1,343.05   $1,343.30