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 $214.86   9.757%   $235.8239   $235.82   $235.80   $235.80  
  Purchase #2 $206.97   10.407%   $228.5094   $228.51   $228.50   $228.50  
  Purchase #3 $18.89   3.716%   $19.592   $19.59   $19.60   $19.60  
  Purchase #4 $104.94   3.723%   $108.8469   $108.85   $108.85   $108.80  
  Purchase #5 $160.53   5.347%   $169.1135   $169.11   $169.10   $169.10  
  Purchase #6 $244.51   3.646%   $253.4248   $253.42   $253.40   $253.40  
  Purchase #7 $53.42   6.258%   $56.763   $56.76   $56.75   $56.80  
  7 purchase totals = $1,004.12       $1,072.0735   $1,072.06   $1,072.00   $1,072.00