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 $182.75   6.585%   $194.7841   $194.78   $194.80   $194.80  
  Purchase #2 $227.44   4.400%   $237.4474   $237.45   $237.45   $237.40  
  Purchase #3 $238.59   7.336%   $256.093   $256.09   $256.10   $256.10  
  Purchase #4 $146.82   3.186%   $151.4977   $151.50   $151.50   $151.50  
  Purchase #5 $155.99   10.838%   $172.8962   $172.90   $172.90   $172.90  
  Purchase #6 $32.54   7.497%   $34.9795   $34.98   $35.00   $35.00  
  Purchase #7 $174.93   7.508%   $188.0637   $188.06   $188.05   $188.10  
  7 purchase totals = $1,159.06       $1,235.7616   $1,235.76   $1,235.80   $1,235.80