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 $231.72   13.770%   $263.6278   $263.63   $263.65   $263.60  
  Purchase #2 $228.81   7.108%   $245.0738   $245.07   $245.05   $245.10  
  Purchase #3 $62.64   10.681%   $69.3306   $69.33   $69.35   $69.30  
  Purchase #4 $229.52   3.283%   $237.0551   $237.06   $237.05   $237.10  
  Purchase #5 $87.63   6.847%   $93.63   $93.63   $93.65   $93.60  
  Purchase #6 $63.70   5.821%   $67.408   $67.41   $67.40   $67.40  
  Purchase #7 $117.33   7.773%   $126.4501   $126.45   $126.45   $126.50  
  7 purchase totals = $1,021.35       $1,102.5754   $1,102.58   $1,102.60   $1,102.60