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 $214.70   7.110%   $229.9652   $229.97   $229.95   $230.00  
  Purchase #2 $84.73   12.477%   $95.3018   $95.30   $95.30   $95.30  
  Purchase #3 $216.94   4.610%   $226.9409   $226.94   $226.95   $226.90  
  Purchase #4 $78.59   9.697%   $86.2109   $86.21   $86.20   $86.20  
  Purchase #5 $98.47   6.104%   $104.4806   $104.48   $104.50   $104.50  
  Purchase #6 $111.41   13.733%   $126.7099   $126.71   $126.70   $126.70  
  Purchase #7 $233.32   13.418%   $264.6269   $264.63   $264.65   $264.60  
  7 purchase totals = $1,038.16       $1,134.2362   $1,134.24   $1,134.25   $1,134.20