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 $167.53   5.141%   $176.1427   $176.14   $176.15   $176.10  
  Purchase #2 $95.66   9.299%   $104.5554   $104.56   $104.55   $104.60  
  Purchase #3 $225.55   4.466%   $235.6231   $235.62   $235.60   $235.60  
  Purchase #4 $204.30   13.834%   $232.5629   $232.56   $232.55   $232.60  
  Purchase #5 $191.56   3.824%   $198.8853   $198.89   $198.90   $198.90  
  Purchase #6 $224.70   3.421%   $232.387   $232.39   $232.40   $232.40  
  Purchase #7 $208.61   10.752%   $231.0397   $231.04   $231.05   $231.00  
  7 purchase totals = $1,317.91       $1,411.1961   $1,411.20   $1,411.20   $1,411.20