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 $59.41   13.337%   $67.3335   $67.33   $67.35   $67.30  
  Purchase #2 $137.86   8.190%   $149.1507   $149.15   $149.15   $149.20  
  Purchase #3 $206.92   9.395%   $226.3601   $226.36   $226.35   $226.40  
  Purchase #4 $90.81   5.560%   $95.859   $95.86   $95.85   $95.90  
  Purchase #5 $133.68   8.851%   $145.512   $145.51   $145.50   $145.50  
  Purchase #6 $248.37   5.113%   $261.0692   $261.07   $261.05   $261.10  
  Purchase #7 $225.30   11.139%   $250.3962   $250.40   $250.40   $250.40  
  7 purchase totals = $1,102.35       $1,195.6807   $1,195.68   $1,195.65   $1,195.80