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 $74.25   12.558%   $83.5743   $83.57   $83.55   $83.60  
  Purchase #2 $168.73   8.781%   $183.5462   $183.55   $183.55   $183.50  
  Purchase #3 $245.43   7.291%   $263.3243   $263.32   $263.30   $263.30  
  Purchase #4 $53.69   9.617%   $58.8534   $58.85   $58.85   $58.90  
  Purchase #5 $240.74   3.295%   $248.6724   $248.67   $248.65   $248.70  
  Purchase #6 $104.67   13.207%   $118.4938   $118.49   $118.50   $118.50  
  Purchase #7 $158.59   7.290%   $170.1512   $170.15   $170.15   $170.20  
  7 purchase totals = $1,046.10       $1,126.6156   $1,126.60   $1,126.55   $1,126.70