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 $108.69   5.140%   $114.2767   $114.28   $114.30   $114.30  
  Purchase #2 $202.73   11.799%   $226.6501   $226.65   $226.65   $226.70  
  Purchase #3 $123.77   12.812%   $139.6274   $139.63   $139.65   $139.60  
  Purchase #4 $51.89   4.258%   $54.0995   $54.10   $54.10   $54.10  
  Purchase #5 $186.86   9.638%   $204.8696   $204.87   $204.85   $204.90  
  Purchase #6 $228.36   9.383%   $249.787   $249.79   $249.80   $249.80  
  Purchase #7 $183.72   6.632%   $195.9043   $195.90   $195.90   $195.90  
  7 purchase totals = $1,086.02       $1,185.2146   $1,185.22   $1,185.25   $1,185.30