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 $215.46   5.462%   $227.2284   $227.23   $227.25   $227.20  
  Purchase #2 $58.71   4.651%   $61.4406   $61.44   $61.45   $61.40  
  Purchase #3 $214.49   6.685%   $228.8287   $228.83   $228.85   $228.80  
  Purchase #4 $150.73   12.518%   $169.5984   $169.60   $169.60   $169.60  
  Purchase #5 $95.31   9.308%   $104.1815   $104.18   $104.20   $104.20  
  Purchase #6 $96.75   9.316%   $105.7632   $105.76   $105.75   $105.80  
  Purchase #7 $217.41   13.214%   $246.1386   $246.14   $246.15   $246.10  
  7 purchase totals = $1,048.86       $1,143.1794   $1,143.18   $1,143.25   $1,143.10