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 $188.53   5.673%   $199.2253   $199.23   $199.25   $199.20  
  Purchase #2 $241.57   8.702%   $262.5914   $262.59   $262.60   $262.60  
  Purchase #3 $218.82   7.816%   $235.923   $235.92   $235.90   $235.90  
  Purchase #4 $32.78   6.264%   $34.8333   $34.83   $34.85   $34.80  
  Purchase #5 $233.70   6.872%   $249.7599   $249.76   $249.75   $249.80  
  Purchase #6 $9.70   3.461%   $10.0357   $10.04   $10.05   $10.00  
  Purchase #7 $160.88   13.592%   $182.7468   $182.75   $182.75   $182.70  
  7 purchase totals = $1,085.98       $1,175.1154   $1,175.12   $1,175.15   $1,175.00