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 $37.76   10.730%   $41.8116   $41.81   $41.80   $41.80  
  Purchase #2 $55.56   11.105%   $61.7299   $61.73   $61.75   $61.70  
  Purchase #3 $147.41   10.320%   $162.6227   $162.62   $162.60   $162.60  
  Purchase #4 $122.43   10.734%   $135.5716   $135.57   $135.55   $135.60  
  Purchase #5 $215.63   3.282%   $222.707   $222.71   $222.70   $222.70  
  Purchase #6 $210.73   8.753%   $229.1752   $229.18   $229.20   $229.20  
  Purchase #7 $92.82   3.481%   $96.0511   $96.05   $96.05   $96.10  
  7 purchase totals = $882.34       $949.6691   $949.67   $949.65   $949.70