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 $236.35   10.614%   $261.4362   $261.44   $261.45   $261.40  
  Purchase #2 $10.56   5.589%   $11.1502   $11.15   $11.15   $11.20  
  Purchase #3 $191.63   5.796%   $202.7369   $202.74   $202.75   $202.70  
  Purchase #4 $22.80   12.554%   $25.6623   $25.66   $25.65   $25.70  
  Purchase #5 $238.66   6.573%   $254.3471   $254.35   $254.35   $254.30  
  Purchase #6 $239.84   9.215%   $261.9413   $261.94   $261.95   $261.90  
  Purchase #7 $228.58   7.238%   $245.1246   $245.12   $245.10   $245.10  
  7 purchase totals = $1,168.42       $1,262.3986   $1,262.40   $1,262.40   $1,262.30