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 $22.56   9.423%   $24.6858   $24.69   $24.70   $24.70  
  Purchase #2 $188.86   10.509%   $208.7073   $208.71   $208.70   $208.70  
  Purchase #3 $199.59   12.479%   $224.4968   $224.50   $224.50   $224.50  
  Purchase #4 $171.70   10.449%   $189.6409   $189.64   $189.65   $189.60  
  Purchase #5 $46.25   10.491%   $51.1021   $51.10   $51.10   $51.10  
  Purchase #6 $169.59   4.824%   $177.771   $177.77   $177.75   $177.80  
  Purchase #7 $152.25   6.140%   $161.5982   $161.60   $161.60   $161.60  
  7 purchase totals = $950.80       $1,038.0021   $1,038.01   $1,038.00   $1,038.00