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 $224.45   9.581%   $245.9546   $245.95   $245.95   $246.00  
  Purchase #2 $196.93   6.331%   $209.3976   $209.40   $209.40   $209.40  
  Purchase #3 $223.51   3.657%   $231.6838   $231.68   $231.70   $231.70  
  Purchase #4 $169.99   5.338%   $179.0641   $179.06   $179.05   $179.10  
  Purchase #5 $221.89   7.847%   $239.3017   $239.30   $239.30   $239.30  
  Purchase #6 $95.49   10.470%   $105.4878   $105.49   $105.50   $105.50  
  Purchase #7 $245.41   12.307%   $275.6126   $275.61   $275.60   $275.60  
  7 purchase totals = $1,377.67       $1,486.5022   $1,486.49   $1,486.50   $1,486.60