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 $68.83   11.725%   $76.9003   $76.90   $76.90   $76.90  
  Purchase #2 $32.45   13.873%   $36.9518   $36.95   $36.95   $37.00  
  Purchase #3 $183.92   12.659%   $207.2024   $207.20   $207.20   $207.20  
  Purchase #4 $233.63   3.231%   $241.1786   $241.18   $241.20   $241.20  
  Purchase #5 $123.26   5.725%   $130.3166   $130.32   $130.30   $130.30  
  Purchase #6 $240.79   13.439%   $273.1498   $273.15   $273.15   $273.10  
  Purchase #7 $73.43   3.234%   $75.8047   $75.80   $75.80   $75.80  
  7 purchase totals = $956.31       $1,041.5042   $1,041.50   $1,041.50   $1,041.50