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 $104.26   11.479%   $116.228   $116.23   $116.25   $116.20  
  Purchase #2 $23.64   13.393%   $26.8061   $26.81   $26.80   $26.80  
  Purchase #3 $243.37   5.273%   $256.2029   $256.20   $256.20   $256.20  
  Purchase #4 $119.73   5.342%   $126.126   $126.13   $126.15   $126.10  
  Purchase #5 $139.51   6.608%   $148.7288   $148.73   $148.75   $148.70  
  Purchase #6 $229.92   8.125%   $248.601   $248.60   $248.60   $248.60  
  Purchase #7 $14.34   5.429%   $15.1185   $15.12   $15.10   $15.10  
  7 purchase totals = $874.77       $937.8113   $937.82   $937.85   $937.70