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 $67.40   5.617%   $71.1859   $71.19   $71.20   $71.20  
  Purchase #2 $209.26   11.375%   $233.0633   $233.06   $233.05   $233.10  
  Purchase #3 $240.28   6.858%   $256.7584   $256.76   $256.75   $256.80  
  Purchase #4 $227.99   9.682%   $250.064   $250.06   $250.05   $250.10  
  Purchase #5 $205.70   8.870%   $223.9456   $223.95   $223.95   $223.90  
  Purchase #6 $195.49   5.174%   $205.6047   $205.60   $205.60   $205.60  
  Purchase #7 $203.92   11.632%   $227.64   $227.64   $227.65   $227.60  
  7 purchase totals = $1,350.04       $1,468.2619   $1,468.26   $1,468.25   $1,468.30