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 $93.56   13.513%   $106.2028   $106.20   $106.20   $106.20  
  Purchase #2 $151.72   13.213%   $171.7668   $171.77   $171.75   $171.80  
  Purchase #3 $242.92   8.108%   $262.616   $262.62   $262.60   $262.60  
  Purchase #4 $203.48   7.751%   $219.2517   $219.25   $219.25   $219.30  
  Purchase #5 $217.76   3.104%   $224.5193   $224.52   $224.50   $224.50  
  Purchase #6 $235.44   13.800%   $267.9307   $267.93   $267.95   $267.90  
  Purchase #7 $216.83   5.736%   $229.2674   $229.27   $229.25   $229.30  
  7 purchase totals = $1,361.71       $1,481.5547   $1,481.56   $1,481.50   $1,481.60