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 $194.95   3.399%   $201.5764   $201.58   $201.60   $201.60  
  Purchase #2 $218.49   10.591%   $241.6303   $241.63   $241.65   $241.60  
  Purchase #3 $26.84   6.317%   $28.5355   $28.54   $28.55   $28.50  
  Purchase #4 $225.43   5.196%   $237.1433   $237.14   $237.15   $237.10  
  Purchase #5 $168.78   7.650%   $181.6917   $181.69   $181.70   $181.70  
  Purchase #6 $22.97   11.271%   $25.5589   $25.56   $25.55   $25.60  
  Purchase #7 $183.71   3.440%   $190.0296   $190.03   $190.05   $190.00  
  7 purchase totals = $1,041.17       $1,106.1657   $1,106.17   $1,106.25   $1,106.10