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 $119.58   11.735%   $133.6127   $133.61   $133.60   $133.60  
  Purchase #2 $107.60   8.204%   $116.4275   $116.43   $116.45   $116.40  
  Purchase #3 $250.54   12.625%   $282.1707   $282.17   $282.15   $282.20  
  Purchase #4 $65.71   3.632%   $68.0966   $68.10   $68.10   $68.10  
  Purchase #5 $90.78   5.316%   $95.6059   $95.61   $95.60   $95.60  
  Purchase #6 $89.60   10.809%   $99.2849   $99.28   $99.30   $99.30  
  Purchase #7 $227.66   11.222%   $253.208   $253.21   $253.20   $253.20  
  7 purchase totals = $951.47       $1,048.4063   $1,048.41   $1,048.40   $1,048.40