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 $107.89   8.466%   $117.024   $117.02   $117.00   $117.00  
  Purchase #2 $219.57   3.425%   $227.0903   $227.09   $227.10   $227.10  
  Purchase #3 $68.38   10.187%   $75.3459   $75.35   $75.35   $75.30  
  Purchase #4 $111.94   9.191%   $122.2284   $122.23   $122.25   $122.20  
  Purchase #5 $180.44   10.228%   $198.8954   $198.90   $198.90   $198.90  
  Purchase #6 $44.34   4.669%   $46.4102   $46.41   $46.40   $46.40  
  Purchase #7 $62.89   4.317%   $65.605   $65.61   $65.60   $65.60  
  7 purchase totals = $795.45       $852.5992   $852.61   $852.60   $852.50