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 $148.71   10.170%   $163.8338   $163.83   $163.85   $163.80  
  Purchase #2 $134.63   5.725%   $142.3376   $142.34   $142.35   $142.30  
  Purchase #3 $210.38   7.299%   $225.7356   $225.74   $225.75   $225.70  
  Purchase #4 $171.44   7.448%   $184.2089   $184.21   $184.20   $184.20  
  Purchase #5 $193.64   8.778%   $210.6377   $210.64   $210.65   $210.60  
  Purchase #6 $63.50   5.366%   $66.9074   $66.91   $66.90   $66.90  
  Purchase #7 $93.65   8.366%   $101.4848   $101.48   $101.50   $101.50  
  7 purchase totals = $1,015.95       $1,095.1458   $1,095.15   $1,095.20   $1,095.00