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 $59.75   12.472%   $67.202   $67.20   $67.20   $67.20  
  Purchase #2 $93.39   8.792%   $101.6008   $101.60   $101.60   $101.60  
  Purchase #3 $183.46   12.689%   $206.7392   $206.74   $206.75   $206.70  
  Purchase #4 $206.44   5.777%   $218.366   $218.37   $218.35   $218.40  
  Purchase #5 $250.31   3.283%   $258.5277   $258.53   $258.55   $258.50  
  Purchase #6 $42.74   10.392%   $47.1815   $47.18   $47.20   $47.20  
  Purchase #7 $241.26   8.655%   $262.1411   $262.14   $262.15   $262.10  
  7 purchase totals = $1,077.35       $1,161.7583   $1,161.76   $1,161.80   $1,161.70