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 $250.54   7.410%   $269.105   $269.11   $269.10   $269.10  
  Purchase #2 $208.95   7.298%   $224.1992   $224.20   $224.20   $224.20  
  Purchase #3 $149.58   8.177%   $161.8112   $161.81   $161.80   $161.80  
  Purchase #4 $233.76   3.402%   $241.7125   $241.71   $241.70   $241.70  
  Purchase #5 $211.55   9.410%   $231.4569   $231.46   $231.45   $231.50  
  Purchase #6 $113.64   8.240%   $123.0039   $123.00   $123.00   $123.00  
  Purchase #7 $183.40   6.536%   $195.387   $195.39   $195.40   $195.40  
  7 purchase totals = $1,351.42       $1,446.6757   $1,446.68   $1,446.65   $1,446.70