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 $192.43   5.248%   $202.5287   $202.53   $202.55   $202.50  
  Purchase #2 $190.81   11.104%   $211.9975   $212.00   $212.00   $212.00  
  Purchase #3 $81.58   7.386%   $87.6055   $87.61   $87.60   $87.60  
  Purchase #4 $85.50   8.399%   $92.6811   $92.68   $92.70   $92.70  
  Purchase #5 $93.46   3.681%   $96.9003   $96.90   $96.90   $96.90  
  Purchase #6 $119.83   12.812%   $135.1826   $135.18   $135.20   $135.20  
  Purchase #7 $186.93   10.242%   $206.0754   $206.08   $206.10   $206.10  
  7 purchase totals = $950.54       $1,032.9711   $1,032.98   $1,033.05   $1,033.00