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 $207.46   8.223%   $224.5194   $224.52   $224.50   $224.50  
  Purchase #2 $207.41   9.494%   $227.1015   $227.10   $227.10   $227.10  
  Purchase #3 $108.70   13.777%   $123.6756   $123.68   $123.70   $123.70  
  Purchase #4 $10.44   10.508%   $11.537   $11.54   $11.55   $11.50  
  Purchase #5 $78.76   13.619%   $89.4863   $89.49   $89.50   $89.50  
  Purchase #6 $237.97   6.434%   $253.281   $253.28   $253.30   $253.30  
  Purchase #7 $166.47   8.592%   $180.7731   $180.77   $180.75   $180.80  
  7 purchase totals = $1,017.21       $1,110.3739   $1,110.38   $1,110.40   $1,110.40