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 $96.65   4.762%   $101.2525   $101.25   $101.25   $101.30  
  Purchase #2 $98.88   8.828%   $107.6091   $107.61   $107.60   $107.60  
  Purchase #3 $183.72   10.242%   $202.5366   $202.54   $202.55   $202.50  
  Purchase #4 $29.30   13.230%   $33.1764   $33.18   $33.20   $33.20  
  Purchase #5 $248.67   6.226%   $264.1522   $264.15   $264.15   $264.20  
  Purchase #6 $185.35   7.295%   $198.8713   $198.87   $198.85   $198.90  
  Purchase #7 $32.95   3.425%   $34.0785   $34.08   $34.10   $34.10  
  7 purchase totals = $875.52       $941.6766   $941.68   $941.70   $941.80