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 $167.25   7.134%   $179.1816   $179.18   $179.20   $179.20  
  Purchase #2 $33.51   12.252%   $37.6156   $37.62   $37.60   $37.60  
  Purchase #3 $179.62   3.577%   $186.045   $186.05   $186.05   $186.00  
  Purchase #4 $182.82   7.631%   $196.771   $196.77   $196.75   $196.80  
  Purchase #5 $148.55   5.494%   $156.7113   $156.71   $156.70   $156.70  
  Purchase #6 $132.41   7.656%   $142.5473   $142.55   $142.55   $142.50  
  Purchase #7 $218.64   7.558%   $235.1648   $235.16   $235.15   $235.20  
  7 purchase totals = $1,062.80       $1,134.0366   $1,134.04   $1,134.00   $1,134.00