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 $210.59   6.597%   $224.4826   $224.48   $224.50   $224.50  
  Purchase #2 $58.78   6.781%   $62.7659   $62.77   $62.75   $62.80  
  Purchase #3 $113.75   9.776%   $124.8702   $124.87   $124.85   $124.90  
  Purchase #4 $170.95   12.613%   $192.5119   $192.51   $192.50   $192.50  
  Purchase #5 $173.45   5.255%   $182.5648   $182.56   $182.55   $182.60  
  Purchase #6 $238.31   11.498%   $265.7109   $265.71   $265.70   $265.70  
  Purchase #7 $51.83   3.527%   $53.658   $53.66   $53.65   $53.70  
  7 purchase totals = $1,017.66       $1,106.5643   $1,106.56   $1,106.50   $1,106.70