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 $114.40   4.323%   $119.3455   $119.35   $119.35   $119.30  
  Purchase #2 $29.51   10.464%   $32.5979   $32.60   $32.60   $32.60  
  Purchase #3 $193.51   11.421%   $215.6108   $215.61   $215.60   $215.60  
  Purchase #4 $68.99   5.663%   $72.8969   $72.90   $72.90   $72.90  
  Purchase #5 $79.76   8.310%   $86.3881   $86.39   $86.40   $86.40  
  Purchase #6 $145.67   12.201%   $163.4432   $163.44   $163.45   $163.40  
  Purchase #7 $237.64   9.578%   $260.4012   $260.40   $260.40   $260.40  
  7 purchase totals = $869.48       $950.6836   $950.69   $950.70   $950.60