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 $95.25   3.443%   $98.5295   $98.53   $98.55   $98.50  
  Purchase #2 $46.76   4.178%   $48.7136   $48.71   $48.70   $48.70  
  Purchase #3 $101.90   5.196%   $107.1947   $107.19   $107.20   $107.20  
  Purchase #4 $32.33   3.398%   $33.4286   $33.43   $33.45   $33.40  
  Purchase #5 $232.71   12.630%   $262.1013   $262.10   $262.10   $262.10  
  Purchase #6 $173.61   9.694%   $190.4398   $190.44   $190.45   $190.40  
  Purchase #7 $129.95   12.583%   $146.3016   $146.30   $146.30   $146.30  
  7 purchase totals = $812.51       $886.7091   $886.70   $886.75   $886.60