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 $23.78   9.820%   $26.1152   $26.12   $26.10   $26.10  
  Purchase #2 $212.50   11.285%   $236.4806   $236.48   $236.50   $236.50  
  Purchase #3 $98.86   11.334%   $110.0648   $110.06   $110.05   $110.10  
  Purchase #4 $193.93   4.392%   $202.4474   $202.45   $202.45   $202.40  
  Purchase #5 $237.49   4.694%   $248.6378   $248.64   $248.65   $248.60  
  Purchase #6 $165.28   5.826%   $174.9092   $174.91   $174.90   $174.90  
  Purchase #7 $60.76   4.667%   $63.5957   $63.60   $63.60   $63.60  
  7 purchase totals = $992.60       $1,062.2507   $1,062.26   $1,062.25   $1,062.20