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 $119.61   11.216%   $133.0255   $133.03   $133.05   $133.00  
  Purchase #2 $173.33   11.317%   $192.9458   $192.95   $192.95   $192.90  
  Purchase #3 $124.42   6.108%   $132.0196   $132.02   $132.00   $132.00  
  Purchase #4 $218.66   13.462%   $248.096   $248.10   $248.10   $248.10  
  Purchase #5 $207.78   9.393%   $227.2968   $227.30   $227.30   $227.30  
  Purchase #6 $93.86   7.206%   $100.6236   $100.62   $100.60   $100.60  
  Purchase #7 $217.46   7.662%   $234.1218   $234.12   $234.10   $234.10  
  7 purchase totals = $1,155.12       $1,268.1291   $1,268.14   $1,268.10   $1,268.00