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 $95.95   11.263%   $106.7568   $106.76   $106.75   $106.80  
  Purchase #2 $237.57   11.156%   $264.0733   $264.07   $264.05   $264.10  
  Purchase #3 $9.37   5.855%   $9.9186   $9.92   $9.90   $9.90  
  Purchase #4 $228.28   5.254%   $240.2738   $240.27   $240.25   $240.30  
  Purchase #5 $58.51   12.612%   $65.8893   $65.89   $65.90   $65.90  
  Purchase #6 $202.77   5.407%   $213.7338   $213.73   $213.75   $213.70  
  Purchase #7 $235.37   6.733%   $251.2175   $251.22   $251.20   $251.20  
  7 purchase totals = $1,067.82       $1,151.8631   $1,151.86   $1,151.80   $1,151.90