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 $190.34   8.629%   $206.7644   $206.76   $206.75   $206.80  
  Purchase #2 $130.39   8.685%   $141.7144   $141.71   $141.70   $141.70  
  Purchase #3 $244.90   11.150%   $272.2064   $272.21   $272.20   $272.20  
  Purchase #4 $228.94   8.640%   $248.7204   $248.72   $248.70   $248.70  
  Purchase #5 $200.43   3.204%   $206.8518   $206.85   $206.85   $206.90  
  Purchase #6 $209.91   12.666%   $236.4972   $236.50   $236.50   $236.50  
  Purchase #7 $126.66   5.484%   $133.606   $133.61   $133.60   $133.60  
  7 purchase totals = $1,331.57       $1,446.3606   $1,446.36   $1,446.30   $1,446.40