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 $209.26   10.767%   $231.791   $231.79   $231.80   $231.80  
  Purchase #2 $216.88   9.495%   $237.4728   $237.47   $237.45   $237.50  
  Purchase #3 $60.68   4.819%   $63.6042   $63.60   $63.60   $63.60  
  Purchase #4 $168.29   12.154%   $188.744   $188.74   $188.75   $188.70  
  Purchase #5 $194.56   5.119%   $204.5195   $204.52   $204.50   $204.50  
  Purchase #6 $208.82   8.652%   $226.8871   $226.89   $226.90   $226.90  
  Purchase #7 $224.28   4.229%   $233.7648   $233.76   $233.75   $233.80  
  7 purchase totals = $1,282.77       $1,386.7834   $1,386.77   $1,386.75   $1,386.80