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 $33.55   3.756%   $34.8101   $34.81   $34.80   $34.80  
  Purchase #2 $212.44   11.836%   $237.5844   $237.58   $237.60   $237.60  
  Purchase #3 $78.90   11.128%   $87.68   $87.68   $87.70   $87.70  
  Purchase #4 $210.79   4.789%   $220.8847   $220.88   $220.90   $220.90  
  Purchase #5 $63.61   3.577%   $65.8853   $65.89   $65.90   $65.90  
  Purchase #6 $238.58   11.202%   $265.3057   $265.31   $265.30   $265.30  
  Purchase #7 $215.45   12.783%   $242.991   $242.99   $243.00   $243.00  
  7 purchase totals = $1,053.32       $1,155.1412   $1,155.14   $1,155.20   $1,155.20