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 $219.42   6.434%   $233.5375   $233.54   $233.55   $233.50  
  Purchase #2 $90.68   4.342%   $94.6173   $94.62   $94.60   $94.60  
  Purchase #3 $211.71   8.197%   $229.0639   $229.06   $229.05   $229.10  
  Purchase #4 $242.79   4.833%   $254.524   $254.52   $254.50   $254.50  
  Purchase #5 $78.54   9.704%   $86.1615   $86.16   $86.15   $86.20  
  Purchase #6 $78.93   9.559%   $86.4749   $86.47   $86.45   $86.50  
  Purchase #7 $194.47   11.690%   $217.2035   $217.20   $217.20   $217.20  
  7 purchase totals = $1,116.54       $1,201.5826   $1,201.57   $1,201.50   $1,201.60